Dr. Matt Walker: The Biology of Sleep & Your Unique Sleep Needs | Huberman Lab Guest Series

[Music] welcome to the hubman lab guest Series where I and an expert guest discuss science and science-based tools for everyday life I'm Andrew huberman and I'm a professor of neurobiology and Opthalmology at Stanford School of Medicine today's episode marks the first in our six episode series all about sleep our expert guest for this series is Dr Matthew Walker professor of neuroscience and psychology and the director of the center for Sleep science at the University of California Berkeley he is also the author of the bestselling book why we sleep during the course of the six episode

series for which we release one episode per week starting with this episode one we cover essentially all aspects of sleep and provide numerous practical tools to improve your sleep for instance we discuss the biology of sleep including the different sleep stages as well as why sleep is so important for our mental and physical health we also talk about how sleep regulates things like emotionality and learning and neuroplasticity that is your brain ability to change in response to experience and we discuss the various things that you can do to improve your sleep everything from how to

time lighting temperature exercise eating and the various things that can impact sleep both positively and negatively such as alcohol cannabis and various supplements and drugs that have been shown to improve sleep we also talk about naps dreaming and the role of dreams and lucid dreaming which is when you dream and you are aware that you are dreaming in today's episode one we specifically focus on on why sleep is so important and what happens when we do not get enough sleep or enough quality sleep we also talk about the various sleep stages and we also talk

about a very specific formula that everyone should know for themselves called qqr T which is an acronym that stands for Quality quantity regularity and timing of sleep four factors which today you'll learn how to identify specifically for you what your optimal qqr is and then to apply that in order to get the best possible night's sleep which of course equates to the best possible level of focus and alertness throughout your days both Dr Walker and I are very excited to share the material in the six episode series with all of you and as we March

into today's episode one I'm sure it will both provide a ton of excellent practical learning for all of you as well as spark many questions that are sure to be answered in the subsequent episodes of this series before we begin I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford it is however part of my desire and effort to bring zero cost to Consumer information about science and science related tools to the general public in keeping with that theme I'd like to thank the sponsors of today's podcast our

first sponsor is eight sleep eight sleep makes Smart mattress covers with cooling Heating and sleep tracking capacity many times on this podcast we discuss how in order to fall and stay deeply asleep your body temperature actually needs to drop by about 1 to 3° and in order to wake up feeling maximally refreshed and energized your body temperature needs to heat up by about 1 to 3° eight sleep makes it very easy to control the temperature of your sleeping environment so that it's easy to fall and stay asleep and wake up feeling refreshed I started sleeping

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also brought To Us by betterhelp betterhelp offers Professional Therapy with a licensed therapist carried out online now I've been doing therapy for well over 30 years initially I had to do therapy against my will but of course I continue to do it voluntarily over time because I really believe that doing regular therapy with a quality therapist is one of the best things that we can do for our mental health indeed for many people it's as beneficial as getting regular physical exercise the great thing about better help is that it makes it very easy to find

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is also brought To Us by element element is an electrolyte drink that has everything you need and nothing you don't that means plenty of the electrolytes magnesium pottassium and sodium and no sugar as I've mentioned before on this podcast I'm a big fan of salt now I want to be clear people who already consume a lot of salt or who have high blood pressure or who happen to consume a lot of PR say foods that typically contain salt need to control their salt intake however if you're somebody who eats pretty clean and you're somebody who

exercises and you're drinking a lot of water there's a decent chance that you could benefit from ingesting more electrolytes with your liquids the reason for that is that all the cells in our body including the nerve cells the neurons require the electrolytes in order to function properly so we don't just want to be hydrated we want to be hydrated with proper electrolyte levels with element that's very easy to do what I do is when I wake up in the morning I consume about 16 to 32 ounces of water and I'll dissolve a packet of element

in that water I'll also do the same when I exercise especially if it's on a hot day and I'm sweating a lot and sometimes I'll even have a third element packet dissolved in water if I'm exercising really hard or sweating a lot or if I just notice that I'm not consuming enough salt with my food if you'd like to try element you can go to drink element spelled LM nt.com huberman to claim a free element sample pack with your purchase again that's drink element lnt.com huberman and now for my conversation with Dr Matthew Walker Dr

Matt Walker welcome Dr hubman it's an absolute privilege and a delight to be back that's right you've been on here before but I have during this episode in this series we are going to go a lot deeper by the way you look very well rested thank you very much I actually slept pretty well last night um despite it being a foreign location um same time zone that helps just astronomically amazing well rather than ask you what a great night's sleep is for you because I'm pretty sure you're going to tell us that there's uh some

individual differences that people need to pay attention to in terms of what is quote unquote optimal sleep let's start off with the basics what is sleep so sleep I think in some ways you can Define as at least in humans and in fact in all mamalian species is broadly separated into two main types of sleep on the one hand we have something that many people will have heard of called nonrapid ey movement sleep or non-rem sleep for short and non-rem sleep has been further subdivided into four separate stages and they are unimaginatively called stages one

through four increasing in their depth of sleep so stages three and four that that's the really deep sleep that we can speak about and I should explain a little bit at some point what happens during that state with in the brain it's stunning it's astonishing so you've got stages one and two light non-rm sleep when you sort of look at your sleep trackers and it has light nonrem deep nonrem and then REM stages one and two that's light nonr stages three and four that's deep nonr and that's non-r encapsulated on the other hand we have

rapid eye movement sleep or remm sleep and it's named not after the um popular Michael styp band of the 1990s but because of these bizarre horizontal shuttling eye movements that occur during this stage of sleep hence the rapid eye movements and REM sleep is the depending on your definition and we'll probably come to this in in uh later episodes It's the principal stage in which we dream but if your definition is quite loose which is any reported mental activity when I wake you up or when you wake up then it turns out that we dream

in almost every stage of sleep but I'll describe REM sleep from here on in as perhaps you dream sleep and I'll make that faux poop so you've got these two types of sleep non-rem and REM sleep they will then play out in this beautiful battle for brain domination throughout the night and that cerebral war is going to be won and lost on average for the average adult every 90 minutes and then it's going to be replayed every 90 minutes and that creates the standard cycling architecture of sleep so whoever is listening to this when your

head hits the pillow tonight what will happen you'll start to go down into the light stages of non-rm then you'll go down into the deeper stages of non-rm sleep and you'll stay there and after about 45 50 60 Minutes you'll start to rise back up again and then you'll pop up and you'll have a short REM sleep period and then back down you go again down into non-rem sleep and up into REM sleep and as I said you cycle through that on average about 90 minutes but I'll come back to that what's interesting however is

the ratio of non-rem to REM within your 90minut cycle is not stable and what I mean is as you move across the night the the the domination of those two types of sleep within the 90-minute cycle changes such that in the first half of the night the majority of those 90 minutes Cycles are comprised of lots of deep non-rem sleep but very little REM sleep but as we push through to the second half of the night now that ratio balance that seesaw balance shifts over and instead we have much more rapid ey movement sleep and

very little deep sleep so when people think about okay I just go to sleep I lose Consciousness my brain is still firstly nothing further from the truth could be the case in in terms of your sleep second your sleep has a very specific pattern that has consequences to real life so let's say that you're someone who normally gives yourself an8 hour sleep opportunity in bed but the next morning based on what I've just told you you say okay well I want to I'm going to get a jump start on the day or I've got an

early morning flight so I'm just going to come up with numbers here I'm not suggesting that this is the ideal sleep schedule by any means but just to make the numbers simple let's say someone normally goes to bed at midnight and wakes up at 8: so there's their 8h hour opportunity but today they're going to wake up at 6: a.m. rather than 8:00 a.m. to get this push on the day how much sleep have they lost well technically they've lost 2 hours of the 8 hour so they've lost 25% but that's not entirely true they

may have lost 25% of their total sleep but because of the strange structure of deep sleep first and then REM sleep later they may have lost 60 70 maybe 80% of their REM sleep so I only make this point because understanding how sleep is structured can have consequences I will come back to the 90 minutes though it's fascinating we've often and some people probably have heard this before it's a 90minut cycle well there's huge variability some people can have a sleep cycle on average that's maybe 75 minutes others 120 Minutes is it consistent within an

individual it is relatively stable within an individual so I would say that the size of the difference from one individual to the next is much bigger than the size of the difference within an individual from one night to the next to the next not unlike a healthy menstrual cycle in a woman which can range from a short is you know 24 days to 31 days and still be considered a healthy cycle that regular but and it will change across the lifespan of course but for a good number of years it's going to be pretty consistent

within a given woman uh and yet Between Women it can vary quite a bit immensely yeah and what's also interesting is that speaking about um some sex specific things there are sex differences so on average men if you look at them will have a sleep cycle that's about 15 to 20 minutes longer than women which on a 90-minute average is actually quite a lot and I bring this point up because you may have seen some of those sort of claims or devices out there well firstly probably on social media and people send me these things

and say is this true which is you really have to structure your wakeup time at these very distinct 90minut on the clock when the clock strikes the 90-minute midnight you know that's when you have to be waking up and you should set your alarm right these the the rational you'll tell me that it's wrong presumably but the rationale of those devices is that one would be better off waking up at the end of a 90-minute cycle as opposed to in the middle of a 90-minute cycle even if it means getting less total sleep because the

argument is that waking up at the end of a 90-minute cycle allows one to be more alert upon waking right that there's something uniquely special about the completion of a 90-minute cycle that will have you Ed out of sleep feeling like an Energizer Bunny kind of that's some of the claims that they and if I were to ask now true or false false so sleep for as much as you possibly can sleep don't terminate that sleep artificially on the basis of anyone telling you that there is this kind of D Vinci Code magic 90 minutes

that's unfortunately not true and I you know I've been guilty of saying you know it's a 90minut cycle and repeating that so if I didn't know any better I would believe that so I'm not trying to you know chasti anyone I'm just simply saying be aware of that and don't worry don't stress about this unique 90-minute cycle and there's some products out there that say they're going to time you on your 90-minute cycle and wake you up I would probably stay a little bit clear of some of those what about going back to sleep you

said to get um as much sleep as possible if I get six hours of sleep and then wake up and I feel like I could go back to sleep would I be better off going back to sleep provided that my work schedule allows for that or um is it the case that after you've gotten a certain amount of sleep it's a good idea to get up and and go I would say that if you feel as though there's still more sleep in you MH there is or I love that this has become biographical instantly it's

going to be a good episode when that happens I would say hold tight stay in bed with an asterisk that I'll come back to and see if you can get get back to sleep and we can speak about different ways of helping you do that but the reason I put a a slight asterisk there is the following if you're then in bed for the next 45 50 minutes wide awake the danger and it doesn't happen to everyone but the danger is that you start to associate this thing called your bed with this thing called wakefulness

and not sleep and one of the things that we do in cognitive behavioral th y for insomnia is we try to prevent you from spending long periods of time awake and I would say it's probably about a 25 minute rule of thumb it's not a rule it's a rule of thumb if after about 25 minutes you just can't seem to catch it and this is happening frequently I would just be mindful of you then starting to build a bonded Association in your brain that your bed is also the place of being awake the analogy would

be you would never sit at the dinner table waiting to get hungry so why would you lie in bed waiting to get sleepy and the answer is that you you shouldn't and so we need to break that Association now there's nothing stopping you however from saying there's still sleep in me I know that there is so I'm just going to get out of bed go to a different room I'm just going to read a book listen to a podcast and then only when I feel sleepy I'm going to go back to bed because my schedule

allows for it that's the best way I would tell you if you still think the sleep that on the table to try and get it back that's immensely valuable uh knowing that there's sort of a conditioned Place effect of of being awake in bed um I must say I get pretty good sleep most of the time there have been phases of life including recently where sleep has been challenging and I notice as I head toward the bed to go to sleep recently the words in my mind are here's the battle Gra like it's going to

be a night of going to sleep waking up going to sleep waking up we'll get to this business of of continuity of sleep a little bit later so we don't have to go into that now but I I should also note by the way that for some people when I speak with them they will and it's just because you mention it it's beautiful they will be saying I I'm so surprised because I am watching television and I'm falling asleep on the couch and then I get into bed and I'm wide awake and I don't know

why and that's because in part you've built this this connection in your brain and it's and when you go into the bedroom that's what we try to do with cognitive behavioral therapy for insomnia you spoke about it as a Battleground that it's almost this adversarial thing which in some ways infers that at that point you feel as though your sleep controls you and it is a miserable feeling and gradually over time what we would do is work with someone and at that point now you control your sleep your sleep doesn't control you and that is

so of Freedom when you get it but sorry I interrupted you oh no uh I interrupted you but um thank you yeah I've prided myself my whole life on being able to sleep anytime anywhere uh I learned it from my Bulldog Costello or maybe that's what brought us together because he certainly had that I'm so sad he's not here around anymore with us CU I would have loved he feels like he is the best sleep Ambassador if there's a post to child for good sleep well he's here in spirit um sleeping um so this is

interesting and I think it's important for people to hear if if you can't fall asleep or if you wake up in the middle of the night and you can't fall back asleep pretty quickly after about 20 minutes or so probably best to get out of bed um so these 90 minutu is cycles that include different types of sleep um prompt me to ask if you were to describe the basic characteristics of each of those four stages of sleep and especially the deeper stages three and four and REM sleep not just at the level of Rapid

Eye movements during REM sleep but in terms of the types of Dreams or the characteristics of of kind of bodily State and you know maybe you just flesh out the physiology and neurochemistry and you know touch on kind of the the uh dream features associated with each of these uh different stages of sleep this just gets so exciting to me and even now when I go into the lab where I look at sleep traces um from my sleep center it I'm am still in awe in bewildered awe of what the brain does so as we

start to fall into those lighter stages of sleep once you get past stage one sleep which is sort of almost the shallows where you're just wading out um then you go into stage two sleep and one of the Hallmarks of stage two non-rem sleep or something called sleep spindles and the way that we measure sleep in a laboratory by the way is that we place you look like a spaghetti monster you've got all of these electrodes on your head you've got things above your eyes and you've got things on your body and we're essentially measuring

three main signals electrical brain activity we're measuring muscle activity and we're measuring eye movement activity and I'll explain why those three things are necessary for me to know are you awake are you in sleep and if you're in sleep which stage of sleep you're in so going into that stage two non-rem sleep we've got these sleep spindles and at that point I'm looking at the electrical signals from your brain what we call the EEG or the electri inogram and these sleep spindles are these beautiful short synchronous bursts of electrical activity and they last for about

a second to two seconds maybe a little longer and they are bursting at a what we call a frequency of somewhere between 12 to 15 Hertz and what that means is that these brain waves are going up and down 12 to 15 times per second that's what our measure is 12 to 15 Hertz and then you go back and your brain at that point has started to slow down now when we're awake your brain wave activity can be going up and down maybe 20 30 40 times per second it's very fast and frenetic it's actually

very chaotic electrical brain activity but as we're going into these lighter stages of sleep then the brain starts to slow down and at that point in stage two nonrem it's maybe going up and down just four to eight times per second so a huge deceleration in terms of brain wave activity but occasionally you'll get these s of it's going and then you'll get these beautiful bursts of these sleep spindles um I actually did I I've never published it publicly or um we did a project called the sonification of sleep and we took these electrical signals

and then we turned them into sound waves and you can actually hear this beautiful sort of this it's almost this beautiful throbbing of a Slowdown in your brain and then you'll hear these spindles almost sounds like that beautiful delicious rolling R in Hindi so this it's just wonderful I'm not sure I can do that R how's it go yeah not too bad not not too bad I mean we're erring on the side of feline but that's okay Andrew um so so coming back to I'm so sorry um coming back to sleep we've gone into light

stage two as I'm trying to desperately hold it together um and we're going down into deeper non-rm sleep now something spectacular happens and this is where I just almost lose it every time I see it the brain now goes back down and it's speed of of oscillation of going up and down is maybe just one or two times per second it's incredibly slow and this is whole brain activity or localized activity this is so we'll come on to this first the way we would measure it is just from these electrodes which are measuring hundreds of

thousands of brain cells underneath them so a good analogy would be let's say you're at a a football stadium and it's Stanford playing Berkeley in in American football and what we've got is a single microphone dangling over the middle of the stadium and that microphone is picking up the summed voices of the 60 70,000 people underneath it's the same thing with when we place an electrode on your head you're measure measuring the summed activity of hundreds of thousands of neurons underneath but we've now started to use maybe 100 200 electrodes on your head and we

can pick these up in local territories of your brain but that beautiful powerful slow brain waves um that were getting during deep non-rm stages three and four it's not just slow activity you would think okay that's that that sounds like the brain is dormant no no no the brain at that point the size of the w waves is almost quadruple maybe 10x the size of the brain waves when you are awake why is that meaning that the brain waves are going up and down very slowly but the size of them which is what we call

the amplitude that is now huge it's epic so think about it you're on the beach and when you're awake the waves are coming in very very quickly but they're small waves and they're coming in in a random fashion but deep slow wave sleep are these kind of Epic things that would happen in Hawaii where you just get these 20 30 foot waves and they're coming in very slowly but they are epically big that is deep slow wave sleep and then what happens is riding on top of those big slow waves are these sleep spindles they

just keep coming so according to the sort of the Sleep sonification project what you would hear now these slow waves would be that that's the slow wave and the Sleep spindle what is it that happens in your brain though to your question to produce these slow waves well let's go back to the football stadium analogy there before the game that's wakefulness everyone is having a different conversation in a different part of the stadium and and you just get this kind of incoherent sort of blabber that's going on that's wake your brain is doing different things

at different sort of locations of the brain processing different information at different moments in time and that's the fast frenetic activity of wakefulness when you go into deep sleep all of a sudden for reasons that we still don't quite understand hundreds of thousands of brain cells in your cortex all decide to unite in their singular voice of firing and they all fire together and they all go silent together they all fire together they all go silent together and that's what's producing these huge big powerful waves so the analogy in the football stadium would be at

this point now and I'll I'll come across to um to to your University Stanford is is is winning and the the crowd is buoyant and all of a sudden the Stamford crowd is singing Berkeley sucks Burkle sucks and they're all uniting the whole stadium cries out at the same time and then goes silent at the same time it's an epic display of coordinated neural activity in a way that we don't see in any other brain State it's phenomenal it's just in all you answered the question I was going to ask which is does the pattern

of brain activity that you just described occur in similar or identical form during any waking States and I think you just said the answer is no meaning if I understand correctly this is a very very specialized brain State unique to sleep unique to a specific portion of sleep and that begs the question what is it doing so it turns out that all of these stages that we'll describe different stages of sleep do different things for your brain and your body at different times of night and it's very understandable that people sort of in the public

will come over to me and say you know how do I get more deep sleep or how do I get more REM sleep and my question back to them firstly is why do you want more REM sleep and they'll say well isn't that the good stuff and I will say well it turns out that they're all important you need all of them but we can come on to let let I'll speak about non-rem sleep functions first and then I can probably I should unpack REM sleep um and then explain its functions but as an overview

what we know is that during deep sleep first you switch over in terms of your body's nervous system to what we call the parasympathetic nervous system that you've spoke spoken about a lot before which is this kind of very quiescent calming state of your body's nervous system the sympathetic nervous system which is very poorly named because it's anything but sympathetic it's very aggravating and activating and um when we're awake that seems to be somewhat more dominant depending on what state you're in but in sleep especially in deep Sleep you shift over into this very strong

parasympathetic quiescent calm State and that instigates together with other things um and we've demonstrated by the way that we published a paper probably about a year and a half ago that these slow waves and these sleep spindles and the cordination of them how well that they're coordinated seems to instigate a signal down into your body's what we call the autonomic nervous system which carries both the sympathetic and the sympathetic nervous system inside of it and forces you over into a parasympathetic state so these brain waves one of the things that they seem to be doing

is transacting a message to your body's nervous system to say calm down quiet down what then happens firstly what we see is your cardiovascular system ramps down deep sleep you could argue is almost the very best form of blood pressure medication that you could ever wish for it's beautiful then something happens within your immune system we're start starting to unpack this but we still don't quite know why these pulsing deep slow brain wavves seem to be a trigger for instigating two things for your immune system firstly it stimulates the restocking of the Weaponry in your

immune Arsenal so that you wake up the next day and you are a more robust immune individual so these are things like tea cells natural killer cells that sort correct all of that good stuff but what's also interesting there's a more recent discovery um it's not just that your body has um put back all of this Armory in place and in fact Amplified it but your body sensitivity to those immune factors has also increased so you've restocked the the weaponry and you've made your body more sensitive to those immune signals and that's why we will

see in probably later discussions your immune system can start to become you know really markedly impaired when you're not getting enough sleep so that's a second benefit of the Deep Sleep um brain wave patterns the third benefit that we've realized is that it's very good at regulating your metabolic system and specifically your ability to control your blood sugar and your blood glucose and if we selectively deprive you of just deep sleep alone and we can do this now very cleverly it's not as though I see you going into deep sleep and I go into your

bedroom and I wake you up and then you go back to sleep and which is how we used to do it sort of 10 years ago now we can use a very clever method where we play auditory tones to your brain but they are of a level that will not wake you up it's what's called a sub Awakening threshold and we determine that and by playing those tones it forces the brain to resurface out of deep sleep so you will still sleep a total eight hours but I will have selectively excised just your deep sleep

and when I do that sure enough your blood sugar ability your ability to control your blood sugar I should say is impaired really quite demonstrably and it's for at least two reasons the initial thing is that your pancreas when it sees this spike in blood sugar it normally releases something called insulin and that insulin is a trigger to your body to say start absorbing the blood sugar so we don't get this toxic or we don't maintain this toxic spike in blood sugar your pancreas when you are underslept and specifically when you're not getting enough deep

sleep does not release the appropriate amount of insulin worse still what we found is that's selectively depriving you of Deep Sleep means that what little insulin is released the cells in your body become less receptive to that insulin so you're not releasing enough of this chemical to say start absorbing blood sugar and the cells that are they designed to do the they stick a straw out into your bloodstream and they suck up the blood sugar they don't respond to the insulin anymore so on both sides of the blood sugar regulation equation you become imper and

then I can give you an example upstairs in the brain one of the things that we found and we'll discuss is that deep sleep helps regulate your learning in your memory functions it helps start to move memories around in your brain and protect them and shift them from short term to long term deep sleep however we've now discovered is critical for drisking your Alzheimer's trajectory it's during deep sleep when you have a cleansing system in the brain that starts washing away the toxic proteins that build up by way of wakefulness and two of those toxic

components are something that we call beta ameloid and Tow protein which are fundamental ingredients in the Alzheimer's disease brain equation so certainly I could then understand based on that Litany of things that I've just provided and those are only a few of what deep sleep is doing you could imagine that's the stuff that I want to get and that's the thing that I need to optim for not true because there is REM sleep I'd like to take a brief break and acknowledge our sponsor ag1 ag1 is a vitamin mineral probiotic drink that also contains adaptogens

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you'll get five free travel packs plus a year supply of vitamin D3 K2 again that's drink a1.com huberman before you talk about REM sleep um what about stages one and two of sleep are those just um kind of the jog into the into the Sprint that is uh deep sleep stages three and four or if I were to Stage the question I'm asking as an experiment let's say I'm an undergraduate or graduate student in your lab and I say um can we do an experiment where we selectively deprive people of stage one and two sleep

only and and then of course the question becomes what do you put in there instead so there's a bunch of other experiments that one would have to uh do but has that experiment ever been done and if so uh what is the consequence of being stage one two deprived um as opposed to just deep sleep deprived so just as you already um elegantly demonstrated that stage one selective deprivation is very difficult because it's a denovo thing you have to pass through to get to the other stages of sleep is stage one the stage of sleep

that I and other people have experienced many times where you're falling asleep and um you start to have a a dream perhaps about walking or running and then you kick yourself away that's right okay oh and I should have explained what happens stage one I love so as we're going into stage one obviously our eyelids are closed but one of the first signs that we know as we're recording I told you we're recording the electrical activity on the head with these electrodes but I also said that we're measuring IM movement activity and as you're going

into light stage one non RAM for reasons that again we have no idea why your eyeballs start to roll in their sockets underneath your eyelids that change that we can start to see we call them Slow Rolling eye movements and they are the Hallmark of you entering sleep and if you are lucky enough to have a partner you can see this you can you know as they're falling asleep you will see these bizarre now granted if they wake up usually the relationship is terminated very quickly because the thing are you next time I'm on a

plane if the person next to me is sleeping I'm going to be the guy kind of like you're a mirror yeah no don't do that I'm the only one who gets away with it cuz I'm a card carrying sleep scientist and even then yeah American Alliance sometimes take some bridge but um so you get these Slow Rolling eye movements and the brain waves start to to sort of slow down again but you mentioned something else and they are called hypnogogic Jer and as we're going into this first stage of sleep I told you that the

principal stage in which we dream is rapid eye movement sleep that's not exactly true because everyone has had this experience that just as you're drifting off you start to have these little mini dreams almost sort of diet or dreams light lit and you you you can almost wake yourself up based on the fracture point of cognition and what I mean is you're thinking okay so tomorrow uh I've got to get to the studio I'm interviewing that desperately annoying British guy M Walker and then there was uh the elephant in the room with a helicop po

the wings on its head and and you almost just think it wakes you up because you think wait wait sorry excuse me go back rewind what just happened that's the point at which you've transitioned over into the what we call the hypnogogic state where you can have these hypnogogic dreams but you also get these JS we don't fully understand what happens but the what we do understand is that as you're going into sleep you start to lose different aspects of your sensory perceptual apparatus not losing the sense of where did I where did they go

and I can't find them but the the the processing of those now many will remain during sleep one of the things that starts to degrade is what we call proprioception and you've spoken about this before which is knowing how your body is sort of positioned in space so it propri reception is fascinating as you're walking with a colleague and you're crossing over a street have you ever had that feeling where you sort of you step off the curb and you're chatting and all of a sudden you have one of those really ugly wobbles where you

can and it's because you had calculated non-consciously and computationally you understood where your foot was in space you understood the velocity force with which it was descending down onto the road below you you had miscalculated the distance and your brain had expected your foot to hit that that road at a certain time and it did not it sends an error signal back up your spinal cord and that's where you get that yeah this happened to me um uh just last weekend I was at the San Francisco Zoo and periodically throughout the landscape of the San

Francisco Zoo they have these kind of squishy surfaces that are seamless with the concrete around them I think this is so kids can play on the the various sculptures there and if they fall it's a little bit more forgiving so I was just walking across this thing talking to the person to my left and I stepped on this now rather squishy surface and all of a sudden I like I don't know how to walk across this thing and I'm you know I've been walking a long a long period of my life and I really had

to pay attention and then and then transition back onto the concrete and could stop thinking about it for a moment and you almost then have to stop the conversation that you were having because it takes over and you switch from non-conscious proceptive and you switch over so the issue is that when you are lying there awake in bed you sense the mattress underneath you you sense the support you're getting all of that feedback signal that I was telling you was absent when you in inappropriately calculated the distance down onto the road all of that is

in place and your brain is saying everything's fine but as we're drifting off into sleep we start to lose that proprioceptive feedback now normally that loss of propri acceptive feedback and sensation of what's going on and where my body is is is is before the loss of consciousness and so you lose Consciousness and that's then thereafter when the loss of propri reception happens and you don't have this sort of you know mental freak out of of propri receptive break glass in case of emergency but sometimes the speed with which those things happen changes and you

start to lose the propri receptive sensation before you fully lose Consciousness and at that point your body says oh my goodness mattress has just disappeared and I'm falling got and that's where you can have these these JS that's that's our current best theory I know we're going to talk a lot about dreaming in a later episode of the series but uh what you just told me forces me to ask at this moment whether or not in dreams where we sense we are flying is that possible because of the absence of proception we we're sort of

we're on the mattress or on whatever surface we sleep on but according to the brain there's uh we're suspended in space is that right yeah so it's it it's one possibility as to why we have those experiences in some ways though it does bring us on to REM sleep during REM sleep and I'll explain what happens in the brain but what you're talking about is something that is even more unique about REM sleep as we go into REM sleep your brain paralyzes your body so you are physically locked into the incarceration of your body why

why would your brain do this it's what we call muscle atoni now I was telling you that we measure your electrical brain activity and we measure your eye movement activity but we also measure your muscle activity why do we do that well as you're going into non-rem sleep that muscle tone decreases but there's still some muscle tone there but as you go into REM sleep in fact just a few seconds before you enter REM sleep I already know you're going into RAM sleep because bang you you become completely absent of muscle toone and if I

were to pick you and I mean I'm I'm probably not going to be able to pick you up out of your bed um based on certain images I've seen on social media um I'm going to if I lift you up you'd just be like a rag doll you'd have no muscle tone whatsoever it's almost like those toys where it's like a donkey that sits up and it's got a button underneath and you press the button whoosh and it just falls down I used to have those as a kid too like the simple things that you

and I had as children that would fate still own a couple of these but they but yeah I need to get a donkey one um in any event um I know what you're referring to so this this muscle and as we call muscle Aon and I think in sort of medicine usually with an a before it means the absence of something so sort of if you're if you have arhythmia absence of normal athm aasia yeah sort of or um and here it's aonia absence of the tone in your muscles why would the brain do this

well the brain paralyzes your body so your mind can dream safely you would imagine how quickly you could be popped out of the Jee pool if just like you described you thought I can fly so you get up out of your bed and you go to the window and you launch probably not going to end well depending on what floor you're on so this absence of muscle tone this physical incarceration that we have is one of the things by the the way that defines REM sleep from when you are awake because if all I was

doing in my sleep lab was recording your electrical brain activity and I was in the other room and I was just looking at your your brain waves as you go into REM sleep I would not be able to tell are you in REM sleep or are you awake why because the electrical brain activity is so similar when you are in REM sleep relative to when you're awake and what that tells us is that REM sleep is an incred incredibly active cerebral condition your brain is just firing away in fact some parts of your brain can

be up to 30% more active when you're in REM sleep than when you're awake stunning particularly emotional brain centers so it's a it's a stunning state of of paradox and that's the reason that we sometimes call it paradoxical sleep your body is completely immobilized utterly inactive but your brain is fervant with its activity by the way people should not worry when I say that you are your your muscles are shut down and what happens is that as just before you go into REM sleep there's a bursting activity that will go up into your brain to

light up your cortex but there's another signal from the brain stem that's sent down all the way down the spinal cord to the Alpha motor neurons in the spinal cord that will essentially create this inhibition it's only your voluntary sceletal muscles meaning that your involuntary muscles things for example such as your respiration that helps you breathe in your heart that's the reason that we you know survive and live another day after sleep so don't worry about that too much with two exceptions though there are two sets of voluntary muscles for reasons that we still don't

know either that are spurred from the paralysis of REM sleep one of them is the extraocular muscles and that's the reason that when you go into REM sleep you can have these darting horizontal movements back and forth those should also have been paralyzed but they're not and then oddly there is a a muscle in the middle inner ear muscle that does not undergo the paralysis and it will also twitch too just like your eyes but I'm getting into the weed so that's what's happening in these different physiological States and to your question when you don't

have any muscle tone whatsoever maybe that is imp part the reason why a you can start to have these dreams of absent gravitational pull meaning you can start to fly it may also be the reason by the way that coming back to proception you can sometimes have that feeling of some people will describe my teeth are always falling out I always feel as though it's a very common thing to to or you feel the absence of clothing on your body and you say I walked out and I was going to this meeting and I realized

I didn't have any pants on and and you forget that proception is also about knowing that your clothes are on you and sensing those clothes you and I can now direct our attention and sense those clothes on us is it also the case that um when we talk about sleep we talk about falling asleep that the sense that one is falling back into their head I um is related to the progressive loss of propri reception in the early stages of sleep or is it just semantics no I often think that that may have being where

it that that notion comes from we why would we not say that I am sometimes people say I'm drifting off into sleep but or I'm about to enter sleep and we say I'm I'm falling asleep now some of that may be that I'm falling into a sort of a deeper and deeper state of a brain wave activity pattern maybe but I actually think you're right now we don't know ultimately the origin of it but I believe it's imp pop because people have this sense of falling hence falling asleep along those lines um I've found that

if I sleep horizontally on a bed or sofa um the sleep is Far and Away different than if I'm fall asleep upright in a chair or partially upright in a recliner yeah um for instance on an airplane now there are a bunch of other things happening on airplanes Bright Lights noises Etc um so it's not a a good experiment to compare those two situations airplane recliner versus uh in bed at night um too many variables temperature especially but um is there any evidence that one's bodily position during sleep or the uh orientation of the feet

relative to the head you know the angle elevated um upward or downward has any impact on the uh pattern of of different sleep stages or uh quality or uh any other aspects of sleep there is a reason for it and we'll probably come on to this at some point when we speak about different methods for Sleep optimization or the new wave of of fascinating sleep enhancement tools has to do with temperature we think that for you to be able to fall asleep and stay asleep you have to drop your brain and body temperature by just

a little less than about 1 degre Celsius or probably two two and a half degrees Fahrenheit and that's the reason by the way that you will always find it easier to fall asleep in a room that's too cold than too hot because the room that's too cold is at least taking you in the right temperature direction for good sleep whereas the room that's too hot the opposite it turns out that the body's ability to dissipate heat what we call Thermo regulation here and Thermo regulation in One Direction which is which is the reduction in core

body temperature is superior when you are lying down versus when you are inclined versus when you are standing up really and in part it has to do with the distribution of blood throughout certain parts of the brain in the distal versus proximal regions meaning sort of the regions that are Clos to the core of your body versus the regions that are further away but your body's ability if we largely take most item items of clothes off you and then we measure the the core body temperature and the way that we do this um it's a

delightful technique it's called a rectal probe and it's neither Pleasant necessarily for the installation of the the the the experiment of doing it and it's certainly not necessarily for the participant but putting that aside for a second they we can measure your core body temperature and we can measure using temperature sensors all over your body exactly what's going on with the blood flow and we can measure how the brain is starting to dis ipate the heat because one of the principal ways that we dissipate heat from our body is by moving blood around the body

when we bring blood into the core of our body we're trapping it in the core and our core body temperature increases when we push that blood out to the surface it goes to these thin sort of capillaries and vessels on the surface of your skin and you start to dissipate that heat and you dissipate it more quickly so your core body temperature drops and the body's sort of vasoactive capacity for Distributing that blood and then releasing that trapped heat from the core of the body is superior when you are lying down and therefore your body

temperature can drop more quickly which is one of the many reasons why it's not as easy to fall asleep when you're sort of at a 45° angle and why the quality of your sleep won't be as good now there are other reasons to just as you mentioned but coming back to position I would say that there are maybe there's perhaps at least two pieces of evidence that would recommend positional differences or positional changes the the first is very obvious if you are someone who is snoring and you have certainly if you have untreated sleep apnea

which is um where you're sort of not just snoring but you'll have an absence of breath that's what the word apnea means here's another one with an a in front of it pinea sort of you know you've heard of pneumonia and it this is about breath and apnea is about an absence of that breath and with sleep apnea not only do you start to have an airway collapsing partially and that's where you get that flutter and that's the sound of the flutter that we're having but then at some point you just hear silence and at

that point the person's stop breathing entirely absence of breath that is much more likely to happen if you are sleeping on your back because when you're sleeping on your back your Airway is giving way to gravity which is wanting to pull the airway down and close it and shut it off so one of the suggestions for people who have snoring or sleep apne is trying as best you can to train yourself out of sleeping on your back now there's lots of gadgets out there that can sort of help and ways can do that the old

school way that we used to do it um sleep apne is more common in men than it is in women but women still have it but if you had a male you would bring them into the the clinic and you would say could you and it's often males who perhaps are carrying excessive body weight and so they're of larger Mass size You' say can you also bring a t-shirt in uh of your wife and it has to be a t-shirt that is that has a pocket on the front and then we would ask them to

wear the T-shirt back to front so it's a very tight fitting t-shirt it's back to front and then you took a tennis ball or a hockey ball in the back pocket and as you're lying there in bed and you turn over onto your back you get this painful signal of the tennis ball pushing you in the back and it gradually I know who came up with this is this Matt was this um Matt Walker's idea this is not me I am not it's clever yeah I should now be on social media I should be changed

to sort of like sleep torturer rather than sleep Diplomat um so that's one recommendation try to stay clear if you're asking me are there certain positions we should stay away from in that circumstance yes it would be the other comes back to something I mentioned during deep sleep when this cleansing system starts to kick into gear in your brain and wash away these toxins from the day what we've found a little bit of evidence and we and the Royal we because I um like you my lab doesn't do um animal research we only do human

research but some animal researchers had discovered that when animals will sleep with their head on the side the the cleansing capacity of the brain is superior than when the animal is sleeping on its back or sleeping on its front and in fact if you look and you would love this project if you go on to Google and you just search for sleeping animals look at the head position and I will guarantee you that many of them if they're naturalistic are animals with their head turned to the side now the cute ones the funny ones are

when a you know a kitten is SPL out on its back and its head is back that's how someone with sleep apne would sort of sleep on their back and but that's very rare we almost never see that so it's very interesting and what they found was that when those heads were in those sort of side positions the cleansing mechanism of the brain was a little bit better it wasn't night or day it's not as though oh my goodness I'm a front sleeper and you know I'm not getting any brain cleansing or I'm a back

sleeper and not I'm not saying that there's no need to take it to the extreme but I I don't think there's any good evidence yet in humans that firstly that's the case and nor is the strong enough evidence to make any recommendations but I just bring it up because it's in the data and it's starting to emerge that if you were to ask me about sleeping position and are there any recommendations those are the two pieces of descriptive advice I would give you they are not prescriptive pieces of advice you mentioned the relationship between temperature

and sleep and we're going to get into that uh in some degree of detail a little bit later because it's so critical but um prior to starting to record this episode we were talking a little bit about yawning um and you told me something really truly fascinating about yawning which was so there are at least four competing theories of yawning that we have and I think there is probably a emerging clear winner um the first theory was that it was just tiredness that yawning is simply a sign of you being tired and it turns out

that that's not true because many people can yawn when they're bored and they are not tired and they've been very well rested so that doesn't seem to be true the next one was one that that seems to be very logical which is it's about trying to rebalance your blood gases and specifically oxygen and carbon dioxide and you would think that perhaps when you yawn with that sort of when you and you inhale a huge volume of oxygen what you're trying to do is pump back up the oxygen in your bloodstream or when you sort of

and the exhale maybe it's about exhaling more carbon dioxide not unlike the physiological size that occur during sleep of a double inhale with a long exhale correct or that one can voluntarily generate for anxiety Management in wakeful St exactly Y and so that was a a theory that maybe you're trying to balance these these blood gases and there was some very clever experiments where they took it individuals and they artificially increased their oxygen uh levels but more specifically they increased their carbon dioxide levels by directionally they tried to manipulate it and they asked did those

individuals start to yawn more because the idea would be if your blood oxygen is coming down and your carbon dioxide is starting to rise if this theory is correct you should start yawning with greater frequency and there was no difference whatsoever that's probably also the reason that you don't see people yawning on a treadmill or when they're going into more of an oxygen debt and higher levels of carbon dioxide so that theory was knocked out the third theory was one of contagion and it's fascinating yawning like several other things has a contagious element to it

so as the audience unexpectedly they didn't know what you were going to say and before you said it you said you told us something interesting about and you did I guarantee you that there will be people listening right now who said oh I just yawned in response to Andrew hubman yawning it is very contagious in part it's the mirror neuron system and you've obviously understand this in depth your brain has this capacity to mirror the action states of other individuals so a good example would be let's say I'm walking out the door now I'm closing

the door with my hand and all of a sudden I'm going to get my hand trapped and you on the other side of the room you are seeing my hand and as soon as I trap my hand and I Yelp out in pain you almost hold your own hand oh because why why why are you doing that it's not just because you know you're trying to be you know compassionate no you have experienced some degree of what I've just experienced how does it do that because your brain has a system inside of it that mirrors

my action States and it's called a mirror system and you can imagine why it's very good to understand the action and emotional states of others for pro-social capacities and all of that good stuff and one of the things that can also happen with this mirror neuron system is that it mimics yawning so when you yawn my likelihood of yawning increases too because my mirror neuron system is matching your Y and what's interesting is that we know other species also have a mirror neuron system and that means that when you yawn there is a statistically higher

chance that your dog will yawn and it's cross species so when your dog yawns there's a higher probability that you will yawn and we've got this St and it's it's very clear one of the other interesting theories though is that when um species that are Cooperative species for example a pride of life Lions when one of those Lions yawns firstly many of the other Lions will yawn in a contagious fashion but then consequently there is a collection of actions that happen after that contagious yawn and so some people have suggested that the yawning is a

way to enact Cooperative group Behavior that's another theory the final Theory number four which I think has the best evidence for is not the gaseous exchange balancing of carbon dioxide and oxygen but when you inhale oxygen from the outside it's usually cooler than your core body and brain temperature and when we inhale there is a modest drop in brain temperature and when the brain temperature starts to rise that's when we see yawning frequency beginning to increase so next time you see someone yawn don't think oh they're bored or they didn't get enough sleep go over

to them hug them and say I know your brain is getting warm it's okay and then at that point the friendship will be terminated because no one should be hooking each other and saying your brain is warm I'm so sorry but anyway that aside um I'm sorry we I took us down that that um tributary of my polluted stream of Consciousness but that's yawning explained those are the four theories and we don't have a definitive answer but I think the best one right now that will continue is that it's about brain cooling that theory makes

a lot of sense um people tend to yawn when they get tired as you mentioned people can yawn for other reasons as well if I'm yawning because I'm tired and yawning is to cool off my brain that's too warm is that an attempt to put my brain to sleep because we need to cool the brain in order for it to go to sleep or something else going on there also and this um sort of merges with the previous question about body position I've lectured in the university for you know well over a decade as I

know you have as well and occasionally every once in a while there's one student I'm just kidding there are several students especially if it's an afternoon class or a very early morning class that is falling asleep in their chair and then their head they kind of jolt awake and we all know that keeping the room a little bit cooler sometimes helps to keep people awake um as opposed to a warm afternoon classroom but in some ways what we're talking about here um violates what you were talking about earlier that it's easier to fall asleep in

a cool environment as opposed to a warm environment uh the brain needs to cool in order to fall asleep but then when we yawn it's in response to the brain being too warm and so um and so I'm I'm having a little bit Circle for me yeah help me understand square square that Circle I like it yeah please square that Circle for me Matt um it turns out that for you to drop your core body temperature the opposite has to happen which is that you have to warm up to cool down to fall asleep and

I mean warm up in a very specific way you have to have the outer surface of your brain warm up you have to get blood to the surface of your skin and that surface is almost acts like a snake charmer that it Dr draws the warm blood from the core and it pushes it to the surface and you radiate the heat out and as you radiate the heat out said your core body temperature plummets so why would people be falling asleep sort of you know in an afternoon meeting when it starts to get a little

warm well in part it's because the warmth of the room is starting to make the sort of face a little bit more Rosy it's drawing the blood out to the surface so what's happening the core of your brain and your body temperature are starting to drop and at that point that's why you're going to start to feel a little bit more sleepy that's reason one the second that you described is that afternoon you know you're in meetings around a table and you start to get as you said those wonderful head nuts and people listening you

you all know that where the of head goes down and snaps back up it's not that people are listening to good music and sort of doing this head bobbing it's that they falling prey to what we know is a genetically hardwired pre-programmed drop in your afternoon alertness it's called the postprandial dip in alertness and that infers that it's after some kind of a a meal it turns out it's not really related to a meal people say well I had a heavy lunch I had sort of pastor at lunch and I always feel sleepy afterwards maybe

in part but if I remove if I prevent you from having lunch and we've done these studies too your brain still shows this very reliable drop and alertness somewhere between quite wide but somewhere between about 1: to 4:00 p.m. in the afternoon yeah for me it's always between 2 and 300 p.m. which uh is a time I'm resisting looking at my watch right now just to see yeah we might be in that in that uh phase of the day uh I can always feel it and um if I close my eyes for 10 20 minutes

um it I usually can fall asleep pretty quickly yeah for a nap I know we'll talk about naps later um but if I don't and I ride it out I then you know usually by about 3 3:30 I'm fine get that rise back up don't you and it sort of swings back up and so that's in part the reason though explaining the yawning and that that warm feeling of I'm in the the meeting room the boardroom meeting and the the the blinds are open the sun is coming through I've got the sun on my back

I'm starting to get very warm but I'm starting to get really really sleepy it's the it's the collusion of two things it's that you're going into this higher frequency sleep Zone in the afternoon this postprandial drop in your brain alertness and we can measure it it's very reliable you can see this dip in your brain electrical activity and you're getting warm at the surface which brings blood to the surface releases that heat from the core it drops and boy do you want to fall asleep I want to take a brief break and acknowledge our sponsor

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tracker's plans again that's insid tracker.com huberman I took us on a bit of a journey into some um I don't want to call them sidebars but some uh specific features around sleep and falling asleep Etc let's get back to the different stages of sleep and frame that under the question of what is great sleep what is mediocre sleep I think we all know what bad sleep is it's when you can't get sleep but I think there's a whole different category of bad sleep that you're going to tell us about which is sleep that we think

is good but is actually not as good as we we think it is I'm always the barer of Doom and Gloom no but well and but also but also the um the deliver of of powerful tools to improve one's one's sleep and thereby wakeful state so along those lines you know what is sleep for truly and what happens when we don't sleep well is perhaps more intuitive to most people you know oh I feel cranky or I can't remember things or I just kind of you know um stress seems to feel a little more intense

the same amount of stress feels more intense um and what is great sleep you know and and and this is I think all under the umbrella of of you know why do we sleep I mean why do we spend a good third to you know or more of our life in in this incredible state of mind and body that we call sleep and it really is quite a stunning state of idiocy when when you consider it because when you're asleep you're not finding a mate you're not reproducing you're not foraging for food you're not caring

for your young and worse still you are vulnerable to predation on any one of those grounds but especially all of them as a collective sleep should have been strongly selected against in the course of evolution and in fact one of the founding fathers of sleep research Alan re shaen once said that if sleep doesn't serve an absolutely vital function it is the biggest mistake The evolutionary process has ever made and now what we've learned through you know almost 10,000 plus research studies over the past certainly 70 80 years now is that nature did not make

a spectacular blunder in creating this thing called sleep so maybe I can firstly address what is what is sleep doing and what happens if we're not getting sufficient sleep and then the other question is what is what is good sleep in terms of what sleep is doing and why he was right in saying that mother nature didn't make a a blunder and it hasn't by the way because if you go back every species that we have carefully studied to date seems to sleep and what that tells us even you know very old evolutionary old ancient

um earthworms seem to sleep they will have a period of what we call theargus which is they seem to be inactive so what I I bring that point up because it means that sleep appears to have evolved with life itself on this planet and then it has fought its way through heroically every step along the evolutionary path and that by itself must tell us that whatever sleep is doing it must be non-negotiable life support necessary in what ways is it life support necessary well we now know many of those first when you're not getting sufficient

sleep I can speak about your hormonal systems let's say I take a group of really healthy young men and I limit them to four or five hours of sleep for five nights they will have a level of testosterone which is similar to someone who is probably 10 years older than them so a lack of sleep will agid you within 5 days by a decade we also see equivalent imp uh imper in female reproductive Health caused by a lack of sleep impermanence in estrogen in follicle stimulating hormone and also in lutenizing hormone what what about the

uh effects of a single night's poor sleep on on hormones um and not to get too down in the details here but uh is it necessary to have four or five nights of minimal sleep in a row before you start to see these effects or let's say somebody's getting good sleep for three nights or four nights of the week but then the other three are kind of challenging for whatever reason does one see a graded effect a kind of intermediate reduction in sex steroid hormones like testosterone estrogen follicle stimulation there is some degree of a

dose response curve but we haven't mapped it out with high so the way I would want to do it as a sleep scientist would say okay I'm going to do this for one night and I'm going to thin slice you to S hours 6 hours 5 hours and then I'm going to do it for two nights and you're going to again be in the 6 hours 7 hours 4 hours and I would like to build up this High Fidelity map and understand that we don't have that but certainly what we know is that a night

of total deprivation will markedly imper those hormones and we know that after about you know a working week of short sleep you see those imp perance too um but let me come back to one night so that's the hormonal system as an example and we've already spoken or I'll come back to it um right now the metabolic system and another hormone um insulin what we found is that if I take you again and I limit your and you're perfectly normal healthy you don't have any signs of type 2 diabetes and I limit you to let's

say 5 hours of sleep for four nights and then I measure your ability to dispose of blood sugar and um your level of blood sugar impairment is so disrupted that at that point your doctor would classifier as being pre-diabetic so I could take an individual and within five nights of short sleep I can move them towards a path that's getting very close to type 2 diabetes and as I said we've UND and we Royal we here um whenever I say we by the way it usually means that um well whenever I say I did something

I mean at my Center we did something and when I say we did something I mean that they did something that's a a fair Shand for uh for attribution um and so so there there have been studies that have really decomposed exactly how that impermanent in blood sugar happens and we mentioned that earlier in this episode I can also then move on to for example your um your immune system this is a very good demonstration firstly there's a great study done by Michael ow and his colleagues at UCLA and he took individuals healthy individuals and

he limited them to just four hours of sleep for one single night and he measured levels of critical anti-cancer fighting immune cells called natural killer cells and what he found is that after that one night of just four hours of sleep there was a 70% reduction in natural killer cell activity that is a striking state of immune deficiency and just to give people a you know a reference point these natural killer cells were think of them almost like the secret service agent of your immune system these natural killer cells they are very good at identifying

dangerous unwanted elements in your body like cancer and going after them and destroying them so you wish for a very verile set of these immune assassins in your body at all times and if you're not getting sufficient sleep that may not necessarily be the case we also know that if you are not getting sufficient sleep in the week before you get your flu shot and this is just another example of how sleep is critical for your immune system if you're not getting that sleep in the week before you get your flu shot you produce less

than 50% of the normal antibody response therefore rendering that flu shot largely ineffective in terms of vaccinating you we also know that if you're not getting sufficient sleep on average let's say that you're getting less than 6 hours of sleep or less on average you're almost three times more likely to develop the common cold common flu and I know that you at the time of us recording this um you've released some fantastic content about the the flu and and the Rhino virus in particular so that's a good demonstration of your immune system we also know

that it's not just that it's also your cardiovascular system that suffers when you're not getting sufficient sleep and here again the data I think is very strong cardiovascular disease RIT large including stroke and and heart attack and there is one study that I think illustrates this and and granted now in terms of the replication the effect sizes may not be as big but the study was interesting they didn't do something radical like depriving you of sleep for an entire night nor did they just limit you to 5 hours of sleep for you know four nights

there is a global experiment sleep experiment that has performed on about 1.65 billion people across 70 countries twice a year and it's called daylight savings time now in the spring when we lose an hour of sleep what they observed in that paper was a 24% relative increase in heart attack risk the following day yet in the autumn in the fall when you gain an hour of sleep there was a 21% reduction amazing in heart so it's bidirectional and by the way and I I said that that paper there are you can there are some aspects

that you can sort of discuss but it has been replicated we see increased rates of hospitalization after that 1 hour of lost sleep in the spring there are higher rates of car accidents on the road after 1 hour of lost sleep we also see higher rates of suicide after 1 hour of lost sleep during the spring time change we even see this is great data they they looked at um the sentencing of federal judges in the United States and because it's the federal system the government system all of those things are cataloged and well documented

you have a huge database and they went back and what they found is that in the spring when we all lose that 1 hour of sleep opportunity those judges doled out harsher Federal sentencing in the day after they had lost one hour of sleep because their emotional and mood states were imper and we'll speak about this in a later episode too so if you are up for sentencing or please try to avoid that spring time change as best you can go for the go for the fall date if if it's possible um so that's that's

your cardiovascular system I could also tell you that it goes all the way down into the cellular and molecular state of your body and this I'm trying to do this to impress the fundamental importance of sleep there was a wonderful study done by my colleagues at the University of Sur back in the UK by led by duk Yandy and what they demonstrated was that if you take healthy individuals and everyone is going to act as their own control and you limit them to um 6 hours of sleep for one week versus allowing them to sleep

at least 8 and a half hours or more time in bed and then what they did was they measured the change in their gene activity profile relative to when those same individuals as I said were getting a full 8 hour plus opportunity in bed versus the 6 hours of limited sleep and they found two interesting things first a sizable and significant 711 genes were distorted in their activity caused by a lack of sleep by the way that's relevant we know that almost one out of every three maybe even one out of every two if you

look at the data people that pass you on the street is trying to survive on six hours of sleep or less during the week so it's a relevant ecological manipulation the second result was that about half of those genes were increased in their activity the other half would decreased now those genes that were imp purred by way of one week of short sleep were genes associated with the immune system so once again you can see this immune deficiency but now playing out at a genetic level those genes that were increased or what we call overexpressed

were genes that were associated with the promotion of tumors genes that were associated with long-term chronic inflammation within the body and genes that were associated with cellular stress and as a consequence cardiovascular disease and to me that study impressed the fact that there is no aspect of your Wellness that seems to be able to retreat at the sign of sleep deprivation and get away unscathed it's almost like a broken water pipe in your home that sleep will leak down into every knck and cranny of your physiology and it will even tamper with the very DNA

nucleic alphabet that spells out your daily Health narrative so I I paint this this picture which seems dire and it I think someone once said to me look your your Ted Talk which I think it was called Sleep uh sleep is your superpower they said that talk should have actually been sleep or else dot dot dot which was a completely fair thing because I think you know very early on as a public figure for sleeper um I did a terrible job I was very dictator I was very disagree um well I was I think I

think I was very absolutist and I've I've learned my lesson I'm I disagree and and um and I'm going to interrupt intentionally uh not to to Puff you up just because but I I think that it's fair to say I know it's fair to say that the cautionary notes that you spoke about in those early TED talks and in your book why we sleep um while they may have stimulated some anxiety for some people uh they absolutely had and have a net positive effect in the sense that they cued people to the importance of this

thing called sleep because prior to you doing that or those things it was the case that it was the I'll sleep when I'm dead mentality um and as somebody who's pulled many allnighters in his career many many um although not these days any longer thank goodness um I can tell you that that information was transformative for for my behavior and also for people in the Arenas of military Sports children adults I I it is fair to say that we have better parents better kids better citizens of every country as a consequence so I I uh

won't allow you one of the few things I'll I you will have a hard line on I won't allow you to U malign your contribution um and the good news is this series is also going to include a lot of discussion about things that one can do anyone can do to improve their sleep so yeah and so enough with that for saying that I will I will stop trying to reject that um but I would also folks put in the comments on YouTube whether or not you agree with me or you agree with Matt and

then um you know uh and thanks for agreeing with me um I would say though that please don't start as you mentioned there you're getting anxious if you're not finding it easy to fall asleep that listen to me is firstly probably not going to make matters any better but don't think even if you're in the general public that look I had one bad night of sleep does it mean I'm now going to develop Alzheimer's disease absolutely not there's we're not suggesting that we're talking about a model in which you know week after week month after

month yes I've demonstrated that you know after just one night of something of short sleep you can see measurable impairments and we can and I can't you know I can't be untruthful about the scientific data but it's not as catastrophic as one may think and as you said in this series we will also speak and focus a great deal about what can you do to start to try to optimize your sleep so thank you for that opportunity absolutely so lots of things not good for us happen when we don't sleep enough on a consistent basis

yes one poor night's sleep let's face it I mean our species would cease to exist if if that were the case because all these parents that have stayed up where you have a you know an emergency or that the neighbor's dog is barking or you you go to an airb B where it's too warm and and you can't sleep I mean um but clearly bad things start to happen when we are chronically sleep deprived we hear less often about the great things that happen when we get great sleep um perhaps we can talk about a

few of those I mean obviously um many of them are going to be the inverse of what you just described but uh for instance learning neuroplasticity the nervous system's ability to change in response to experience uh sleep deprivation impairs learning yes yeah um and a great night's sleep makes it a lot easier to learn right so what are the data in terms of the relationship between sleep and learning again something we're going to go into in quite a bit more detail but can you give us a um uh can you can you throw us a

bone about some of the can you incentivize us for getting good sleep not just through fear but we heard the sticks um you know throw us a carrot yeah so there are so many wonderful carrots so when you are sleeping your brain's capacity and its Learning Centers are so much more ready to absorb information so think about these memory centers in the brain almost like a dry sponge if you've been sleeping well and they are so excited to soak up new information and retain that information so firstly sleep before learning is going to help you

acquire and imprint new memories very effectively and we've demonstrated that we I'll tell you about the studies in in a later episode we also know though sleep after learning does something delicious it will take those freshly minted memories and it will consolidate them into the brain meaning that it will start to fixate them almost like sort of setting them in concrete into the brain and so you are far less likely to lose those memories which is to say you are far less likely to forget if you've been sleeping after you've learned it's not just that

though sleep does more than simply strengthen those individual memories sleep will start to Crosslink and connect those memories together and as a Consequence the next day you will wake up and those that memory back catalog has now been updated with all of the recent information and it's integrated and it's Associated so you are now able to come up with new Creative Solutions to issues or problems that you've been facing because you've updated what we call the associative networks in your brain and this is the reason that people will describe having had these insights by way

of sleep and these problem solving capacities and really that's what to me a good student is not simply a student who can learn all of the individual wrote facts and then just regurgitate them an individual memory is not as sitting as an isolate island is not particularly useful that's why your laptop isn't well as long as it's not connected to the internet and and uh open AI it's not particularly intelligent I mean it has a storage capacity that is almost more perfect than your brain it doesn't make some of the the memory sort of mistakes

that we do the reason it's not as intelligent as we are in part is because it has not integrated the information it doesn't link all of the wouldn't it be wonderful if you woke up one day and you'd installed a program on your computer and your computer just understood how all of the files were interrelated and connected and it was saying okay you you know you've double clicked on this file well now I'm going to tell you that there is this related information you should pull this in here and it would enhance this paragraph that

you're working on or it would improve this experimental idea that you're coming it doesn't do that but your brain does that how does it do that in part it's because sleep is building these associative networks so it's not it's not simply the student who learns the rote facts it's the student who learns the facts and then understands what they mean sleep is not just about learning and it's not just about knowledge it's about wisdom which is knowing what it all means when you fit it together and that's one of the other roles of sleep so

those are some of the beneficial things the sort of the the carrots that can come by way of for your learning and memory there are so many other carrots though we described for your immune system how there is this restoration that happens during deep sleep and it primes that but there are other benefits too one of the things that we've discovered and we hopefully we'll get to discuss this in more detail is that sleep provides almost a rebooting of your emotional and your mood States and as a consequence you wake up the next day and

you are dressed with a very different set of emotional clothing and sleep when you're getting it almost it's like a set of emotional windscream wipers that it's just cleared those things off and you wake up it's the reason that people will tell you you know you if something is troubling you don't worry just come back tomorrow just give it a night of sleep and you'll probably feel better tomorrow that feeling better notion is sleep acting as this emotional bomb that just soothes that those Jagged edges that we've you know be sort of almost like a

CD getting scratched if anyone out there knows all a CD is these days but you know these scratches that we get emotional wounds sleep is starting to heal those as well so those are benefits I could also mention some other aspects of your weight control and your weight gain and this is a huge huge effect size Sleep moves the needle on almost every aspect of brain and body health I think it's very clear at this stage that there is no single tissue or major physiological system in your body and no operation of your mind that

isn't wonderfully enhanced by sleep when you get it or demonstrably imper when you don't get enough but when it comes to appetite and regulation of weight gain this is immense firstly what we know is that when you're getting sufficient sleep you can create a a nice um concentration ratio of two appetite regulating hormones called leptin and grin and let me go sort of in the reverse to probably give you a better example let me say I deprive you of sleep and what we see is that these two hormones that and I joke you know that

sometimes sound like um leptin and grin sound like Hobbits from Lord of the Rings but they're not they're real hormones and leptin essentially is the signal that tells your brain okay your you're satiated by your food you're full and you don't want to eat more so hunger and appetite decrease grin does the opposite when grin increases now it's the signal of hunger and you get increasingly unsatisfied despite eating a f full meal if you've got still high levels of grin you don't feel satisfied with that meal and many people listening may start to say I

have this feeling where I'm just eating and I just don't feel satisfied on some days and those days I suspect can be days when you are not sleeping well and I think everyone has had this feeling of saying I just didn't sleep well last night and I I just get ravenous and my I just unleash this Unholy hunger and an appetite that's in part because these two hormones so what happens is that when we're not getting sufficient sleep leptin the signal that says you're satisfied with food stop eating that is imper by way of a

lack of sleep if that wasn't bad enough the hormone grin that says no you're not satisfied with your food eat more that's the signal of hunger that increases so it's almost like double jeopardy you're getting punished twice for the same crime of not sleeping once by way of a drop in leptin stop eating and once by way of growling foot to the floor acceleration I want to start eating that's in part why you're going to your waistline can start to expand when you're not getting sufficient sleep but when you do it's a it's a fantastic

way of controlling I guarantee you if you start to implement better sleep your ability to regulate your basil levels of appetite and hunger will decline but it's not just that you want to eat less or you at least want to eat an appropriate amount for your body mass it's also what you want to eat and what we've discovered is that when you are again not getting sufficient sleep you start to eat more more yes you do but you eat more of specific things you crave things like these heavy hitting sort of stodgy carbohydrates like bread

and pasta and potatoes and pizza and also you crave simple sugars and so those Foods we know in excess can be what we call obesogenic Foods they are foods that can lead you to a more rapid amount of weight gain whereas when you are getting sufficient sleep now you're reaching at the food bar for you're saying what I think the the salad and those healthy nuts and the fruits and those things look quite appetizing today versus when you are underslept all you want to do is go after the junk food and because you kind of

got these Munchies what's interesting is that a recent discovery came back to that notion of the munchies when I say I got the munchies people sometimes think of a drug reference they'll say well been smoking weed I always get the munchies why is that because when you when you are bringing in cannabis into the body and these canabo these what we call exogenous canabo they will increase your appetite they will stimulate your appetite cannabinoids are appetite stimulating components but we all have our own version of cannaboids that we produce inside of our body that you've

spoken about before called endoc canabo when you are underslept the brain releases more endoc canabo and that's in part why you get this strong impulse for and thus IO when you start sleeping better you moderate all of these hormones and these chemicals and your appetite is controlled when you eat you feel satisfied with your food you're not craving more when you make your food choices you're making better food choices we did a study with brain Imaging where we underslept individuals and we had them see food items inside of a brain scanner and they had to

rate you know how much do I desire and how much do I want these items and those items range from very healthy items all the way to unhealthy items things like ice cream and sort of pizza and all of that good stuff and sweets um Candy as you would say over here and we looked at their ratings and by the way we to make this a more ecological because you could say Well they're going to know what's the healthy choice so they're probably just is going to be you know politically correct and say oh I

desire the healthy food because the way that we tried to get around that was we said anything that you said was desirable when you come outside the scanner we've actually got all of these foods and you're going to have to eat them um so they were making more real realistics and each person went through the experiment twice one night after full nights of sleep one night with significantly less sleep and sure enough inside of the scanner they were rating unhealthier Foods as more desirable so your preference was going in that unhealthy Direction but what was

interesting was what was going on in the brain we saw that the frontal lobe regions these sort of areas that sit above our eyes that almost act like the COO of the brain and they help regulate our deep emotional centers those regions of the brain had gone offline by way of a lack of sleep and these emotional centers that are usually associated with more honic reward and they're also excessively more active in people with obesity who have what we call honic eating patterns those regions were ramped up by way of a lack of sleep so

it's not just that there are chemical changes in your body that conspire to have you eat more there are also changes in your brain that prevent you from making the healthy food choices but when you're getting sufficient sleep in the control condition when they were getting that sleep their brain was beautifully regulating the optimal food choices so that that's just another example of a carot carrot no pun intended now um that when you're getting sleep if one of the ways you want to manage your your body composition and manage your appetite is by way of

getting sufficient sleep it's actually a very powerful tool that we probably underrate and then this other aspect I would say is emotional and mental Wellness everyone knows that your emotional and mood States will take a nose dive like a Dart into the ground when you're not getting sufficient sleep it's that idea of I just snapped dot dot dot and those are the words that usually you know are uttered by people who are not usually sleeping very well but when you're getting good sleep it's so much easier to regulate and manage those emotions and Michael Grand

know great sleep research he did an interesting study and it was one of those studies many studies I read from my colleagues that my initial reaction to the study was jealousy because it was such a good study and I was jealous that I didn't think of the idea and now gradually with my senior age I've disabused myself of that ego and very quickly I then think this is the best favor and I can't wait to tweet it out but he did a great study and it was only quite recently he asked what are the reasons

that people want to try to improve sleep you would have thought that we'd have known this you know decades ago and it's a relevant question to the point that you're asking which is about these carrots I know that there is still probably some degree of a sleep loss epidemic out there in the world there is still that sleep machismo mentality that I can sleep when I'm dead so how can we try to motivate people well I can do it with the stick and I can do the whole sort of you know if it bleeds it

leads and do the Doomsday stuff and that can that can motivate but why don't I try to understand what it would be for most people that would have them try to enact better sleep behaviors and they asked all sorts of different options and the two things at the end of the paper when they did all the statistics that stood out like two sore thumbs I want to try to improve my sleep because I want to improve my mood I want to improve my sleep because I want to improve my body weight people know it they

already knew it we didn't have to show them the data and so it's just interesting so I'm just bringing those two things up as a as carrot examples there are many others of course too terrific examples of carrots for uh that one can get if they get adequate sleep and we'll talk about quality and some other features of sleep that are important in just a moment but I'm curious how come when we are sleep deprived um we get bags under our eyes and our skin Health shows it like even one day you know if you

know someone well and you see them regularly and they walk in and they they look particularly well rested yeah we you know we think they're you know kind of bright-eyed and bushy tailed um so to speak um but you can often see it in their skin and in their eyes how glassy their eyes are how open their eyes are but also the bags under under their eyes and of course folks um never say to somebody um you look tired um it's it's a the other way to um do it is just if if they look

particularly well rested on a given day say you look well rested actually I told you that today you did that's right I would have forgot about that but now I remember um and and it's true you look very well rested being the the Sleep guy and all um why do why do we show our lack of sleep in our skin so rapidly it's almost like a a thermometer on on how much sleep somebody got the night before it it's stunning isn't it and you can almost see it you know if if you have a partner

and they come through to the sort of kitchen in the morning and they look at you and because you're so familiar with that face because it's a face that has imprinted on you thousands of times you can notice subtle changes and you can sometimes sense you know they they do look tired but you're absolutely right you don't you don't say that you just say oh you know how are you this morning and is there anything I can do for you should I make you a coffee maybe you should go back to sleep and yeah yeah

I think that's the that's the politically incorrect indirect way of saying boy do you look tired um two things on that that front the first it comes back to the immune system that that sort of pale paror in a face almost that sickly looking skin in PO is because you're already seeing the effects of the immune system and it's the same with the bags under the eyes that part of this reboot of the human being you know that human beings seem to have what I would describe as a recycle rate and it seems to be

about 16 hours that after about 16 hours of wakefulness we need about an 8 hourish and it's 7 to n hours is the recommendation don't get hung up on we'll speak about exactly that in a second but it's that seems to be required to reset this whole panoply of of health and physiology of a of a human being one of the things is the immune system and you get this sickly look about individuals and you get the bags under the eyes so that in in part explains it there was a great study done by um

a colleague of mine Tina sundelin and um working out uh in Sweden uh at the kolinska and this again was one of those studies that I just thought was so genius and it was a two-part study they firstly took individuals and they sleep deprived them for a night or they allowed them to sleep well in fact they went through both of those and after a full night of sleep or after a night of sleep deprivation they went into a studio and they had the picture taken they had a portrait shop done under identical lighting conditions

so now for every participant in the study you've got two head shots one of when they were sleep deprived one when they were sleep rested great now came the second part of the experiment they then took all of those kind of head shots and they recruited a new set of participants who acted as an independent set of judges and those judges knew nothing about the experimental conditions and the manipulations that had just happened they were simply shown these images and they were asked to rate how attractive does this person look how healthy does this person

look and how tired did does this person look and again they knew nothing about what was going on sure enough with very high statistical probability when the the head shot that was taken when they were underslept they rated that indiv idual as looking less attractive as looking more sickly in terms of their appearance and also looking more tired so first they had proven this thing called beauty sleep that you look a more attractive version of you when you are getting sufficient sleep but they also noticed this sickliness sort of composition to someone's face so that's

a very long way of explaining the bags under the eyes I'm sorry I go off in these tangents Andrew and not a mentioned at all I asked you answered and um and here we are okay so you've been explaining the different dimensions of sleep the underlying physiology some of the psychological and physiological consequences of getting not enough sleep enough sleep Etc I think a question that everybody is asking themselves is a how much sleep should they get and B what is really great sleep and then of course there are all these other parameters of sleep

you know leaving aside whether or not one sleeps you know a little bit reclined or on their side Etc you know how should we think about this activity that you're calling sleep you how should we break it down what are the variables that we need to think about in terms of being able to ask ourselves how well or poorly we're doing and for lack of a better way to put it to optimize our sleep so I think to me the question of what is good sleep at at first it seems to be obvious you can

come through again to your partner in the morning and they'll say how did you sleep and you have an answer you know I slept well or I don't think I did sleep well so we all have some subjective sense but science for the most part um science and and medicine has usually used a singular rub rubric which I think is reasonable which is quantity so you would hear that okay how much sleep do we need and what would that look like to be good sleep and the answer is it's a quantity ative answer somewhere between

7 to 9 hours well actually I would answer it differently if someone said um how much sleep does an average person need I would say about 90 minutes more if you look that's the answer you would give every yeah yeah how much sleep do I need and I would say probably about 90 minutes more if you look at the average data but setting that 90 9 90 more uh if you look at based on the epidemiological studies of how much people actually are getting but that metric of quantity is the way that most of us

and I've been you know certainly party to this as well have answered the question as what is enough sleep or what would be a good amount of sleep and good amount of sleep would be somewhere between 7 to n and that's the current recommendation that's the recommendation by many health organizations including here in the US which is the CDC they recommend or they stipulate a minimum of 7 hours for the average adult to me however that doesn't capture the true complexity that sleep really is and it is as we've now discussed in the episode a

wonderfully complex um ballet of of of physiology and so I've stepped back and i' really tried to think to me what are the main components that would constitute this recipe for good sleep and I've conceptualized what I would describe as the four macros of sleep that there are you know we think of diet that we've got three macros fat protein and carbohydrate for me sleep actually has four macros and you can remember this by the acronym qqr T and it stands for quantity quality regularity and timing qqr T quantity quality regularity and timing and maybe

I can just go into detail because I'm telling you you know these are the the rules for good sleep no one responds to rules they respond to reasons and not rules so let me explain the reasons behind each one of these so quantity we've already spoken about somewhere between 7 to9 for the average adult let me move on to Quality we measure quality in a variety of different ways the first principle quality measure of sleep is continuity so meaning was your sleep nice and continuous and you didn't wake up many times or was your sleep

fragmented and littered with many Awakenings it was punctuated by these these Awakenings if it's very highly fragmented that's what we call poor quality of sleep that's low efficiency of sleep so maybe you would be in bed for let's say 9 hours and you still got 7 hours of sleep so if all you used was your quantity measure you would say well you've still had good sleep you've had 7 hours but two of those hours have been spent awake summed total so that is very low quality of sleep and it's what we would call a low

score of efficiency so if you're looking at any of your sleep trackers that's probably best captured by Sleep efficiency what is sleep efficiency sleep efficiency is simply calculated as of the total amount of time in bed what percent of that time will you asleep so if I was in bed for 8 hours and I slept for 6 hours I would have a sleep efficiency of 75% because two out of the8 hours 25% of that time I was awake and an efficiency that is 85% or above we typically classify as healthy sleep and we would like

to see you there or perhaps a little bit higher if you have a lower sleep efficienc score than that it usually means that you're awake too much of the time and we'll think about that and address that so that's one measure of the second Q of the qqr T that's quality but there's another measure that we can also use that measure comes back to the deep sleep that we spoke about and particularly the electrical quality of those brain waves so you can have deep sleep and it can be of different qualities electrical qualities you can

have deep sleep that is is immensely powerful with huge epic waves or you can have deep sleep that still is classified as deep sleep but it's a little bit more sort of anemic in its quality and you can't really measure that with these sleep trackers we have to use electrodes and then we decompose the electrical brain activity using a fancy equation and that tells us what was the amount of sort of strength of activity what we call electrical power in that deep sleep regiment so that's another measure that we use for Quality next is regularity

regularity and actually I should come back to to Quality for a long time in sleep science we were using quantity as our major metric for predictability meaning I look at your quality and does it predict your learning or your memory I look at your quantity and does it predict your blood sugar regulation I look at your Quant quanti does it predict your immune health I look at your quantity and does it predict your mortality risk and the answer has been yes that it quantity does predict many of those things that's great what was interesting is

that if you look at the statistic of the predictability of quantity alone it was strong it was significant but it still left a lot of unexplained what we call variance so the it must be that there is some other things in sleep that are explaining these Health metrics in addition to quantity and quality has now come online I think in the past 10 years as carrying as much if not perhaps even more in certain domains of a predictive strength in determining your mental and your physical health that quantity has and it at least forced me

in my own research to a always be me measuring quality in as high resolution as I can and always including it into a statistical model and we can do fancy things where we put those two things you know pit them head-to head and see which one actually holds more of the statistical weight but certainly quality sleep is as important I would say now at least as important as the quantity of sleep now you can't short Change on either you can't say okay did he just tell me that I should not worry about how long I'm

sleeping but as long so you can't just get 4 hours of sleep that is incredibly good quality and get away with it but you also can't be in bed for 9 hours or 10 hours getting 7 hours of sleep but it's really bad quality of sleep you have to get both you can't short Change either one of those so at that point you think well isn't that the end of the story The QQ why do you need this R and T of qqr t the the regularity has come online I would say in the past

18 months as being a relevant metric when I say you you would say well hang on a second regularity and timing they sound like the same when I say regularity I mean when you go to bed and when you wake up if you keep that consistent that is the third piece of the the four macros that's regularity I go to bed at the same time I wake up at the same time plus minus how much so I would say plus or minus you know 30 minutes you kind of that's your wiggle room you don't want

to try and everyone you know even I I have a I'm thly puritanical about my sleep not because I want to be some post a child and practice what I preach it's simply that if you knew everything I did about sleep it's an entirely selfish act to prioritize my sleep I don't want to die any sooner than I have to and I don't want to live with disease any longer and the greatest health insurance policy that I know of that is universally available largely free and mostly painless is this thing called the night of sleep

so I'll gift it to myself every single night I don't see it as selfish because of course uh when we are ill or dead um there is a burden on others um it's it can be an absence burden or a or a presence burden depending depending depending on what and how people please look at me when you say presence about us but um that's interesting now when you say uh same wake up time same to sleep time plus or minus 30 minutes for each of those uh is that plus or minus 30 minutes uh getting

into bed or are we talking about falling asleep entering that first stage one it's really from the time of lights out so okay I've been in bed and you know I I got into bed at the same time but last night I went to sleep about an hour later and then the night before you know I I got into bed I just turned the lights out and and then you know two nights ago I got into bed again at the same time but then I was kind of online shopping and I started chatting with a

friend in a different time zone and then it was 2 and a half hours later before lights out that is what we would classify as irregular sleep and the reason that this this has really been forced on me as important there was a great study that came out maybe I'll get this wrong from about 5 months from the time of filming this ago and it was it used a huge database something called the UK biobank which is a wonderful database and they looked at over 60,000 individuals and they looked they were able to track the

sleep from one night to the next to the next to the next so they had some Metric of this consistency this regularity and then they split those 60,000 individual into quartiles and in the St statistical model they looked at people who were most regular versus people who were least regular and they tracked them over years what they found and then they looked at their mortality risk How likely was it that those people would pass away during that study inter uh interval and they were also able to map what were they dying of if they passed

away so what they found was that those people who are in the top quarti of being most regular relative to those people who are highly irregular if you had good regular sleep you had a 49% reduced risk of mortality relative to someone who was very irregular of that General allca mortality risk when you split it apart there was um a 35% decrease in cancer mortality specifically and there was almost a 60% drisking of cardiovascular mortality risk if you are regular versus irregular then they did this brilliant thing because they were measuring both the quantity of

sleep and when these individuals were sleeping they did what I just said which is they put them into a statistical model sure enough the quantity of sleep just as we've shown time and in time again was very predictive of all cause mortality using that sweet spot of 7 to n hours and we can speak about what happens when you start to sleep longer because it's it's actually very unpredicted and it's very interesting but sweet spot of 7 to9 the shorter your sleep the shorter your life that's what the data seems to suggest but what they

found was that that was true yet regularity or irregular sleep carried almost twice the effect size the magnitude of predictability that duration did and I think the whole field we knew that regularity I knew that regularity was important I don't think we understood how important and the strength of mortality drisking if you're regular or increased risk if you're irregular that this metric of R carried in the qqr T equation so I've started to be much more mindful myself at least and almost over index that um the final aspect comes on to timing and I should

say that we've we've used this essentially this kind of equation this sleep algorithm as it were of qqr now in a lot of my work in the past at the Sleep Center in the past four or five years and it does seem to be a pretty good proxy of covering predictive wise many aspects of your health that if you use any one of these by themselves yeah they they help they predict things but if you use them as a collective that seems to be where you explain most of the variant now it's not a by

far a perfect measure there are even more nuanced ways that you would want to split it and I want to split it but I would say that this is a pretty good proxy for the general public and it seems to be in our research a pretty good proxy for for health and wellness too the final aspect of the qqr quantity quality regularity comes on to timing how is timing different to regularity because regularity is about getting your sleep at the same correct time what I mean by timing is your chronotype so people may have heard

of this phrase are you a morning type evening type or somewhere in between that it turns out is and it's about a third third split across the population maybe a little bit different does it divide up any differently according to male female and here I'm presumably we're not talking about children or teenagers that's a whole other business and we'll talk about that yeah yeah so once you are an adult and that because that pattern of your timing of sleep does change during development very much so despite you know we can all remember being kids and

wanting to stay up with the grown-ups and and all of a sudden the last thing we remember was you know 7:00 comes around 8:00 comes around and you think great we're I'm going to stay up until 10: or 11:00 with them and then you wake up the next morning cuz you were carried to bed cuz she was lights out so setting that aside once you're an adult and you have your stable rhythm in place um it there there is variability now in sleep science we break it down not into three categories but five extreme morning

type morning type a neutral evening type extreme evening type could you repeat those again so extreme morning extreme morning type so what what qualifies as extreme morning type so an extreme morning type would someone who would like to say go to bed around uh 8:00 p.m. and then they would be you know waking up and they wake up very easily around 4: 4:30 a.m. in the morning and they're bright as a bunny they are ready to get to the gym and I'm a neutral I just sit right in the middle so I'm kind of an

11 to 7:30 kind of guy okay maybe we could walk through the so the extreme morning type is um around 8 and they could be they could wake up at let's say 4: 4:30 and they would be fine um a a morning type maybe they would like to go to bed around 9:30 and then they're waking up closer to sort of 5:36 then you've got a neutral like me and I would like to go to bed probably around 11: p.m. and wake up around sort of 7:30ish I try to give myself about an 8 and

a half hour time period in bed um and then you get get to the um the night owls um so then you've got the evening type and then the extreme evening type which finishes out the 4 five the evening type maybe they would like to go to bed like 12:31 and probably wake up around maybe 9 9:30 and then you've got the extreme evening type and they are not ready for bed until maybe 2:30 3:00 a.m. and they're waking up you know middle of the morning so what's interesting about your chronotype and by the way

people you can if you want to find out your chronotype if you want an actionable suggestion you can just um go online and you can search for something called just type in chronotype meq and that stands for the morningness eveningness questionnaire meq just type in chronotype meq and you will see you can fill it out it takes 3 4 minutes series of questions and it will give you back a score and that will then bucket you into these different flavors and sort of say okay I've tried all of these and you okay and I I

hate to admit it but if I had my preference I would go to sleep at 8 8:30 and wake up at 4:30 or so well let me ask ask you this question because rather than doing the meq I there's a single question I normally ask and say okay Andrew I now put you on a desert island alone and alone you you've got nothing to wake up for no electricity no responsibilities no nothing what time do you think your body would like to go to sleep and wake up and I say that specifically because if I

ask you what time would you like to you're still biased in your head by all of the trappings of society and this terrible towards morning types do you think that naturally that's probably the regiment that you would do yeah great question I would go to sleep sometime between 90 and 120 minutes after Sundown yeah okay so that's why I I was going to answer I'm either an extreme morning type or a morning type I can go to bed around 9:30 wake up at 5:00 feeling great um or go to sleep early 8 8:30 wake up

at 4:00 and really want to get up and write and exercise now that's not the schedule I follow I may uh start to follow that schedule I've tried for various um portions of my life but typically I end up defaulting to going to sleep a bit later 10 10:30 waking up around okay 6 630 and that's assuming that there are no events in my life that are disrupting my sleep because then I'm really going to sleep in if I can and a bunch of things to try and complate but assuming everything is cool in life

um and in the room that I sleep um that's the spirit there you go I would say going to sleep at 9 and waking up at um yeah about 4:35 a.m. it feels great in fact I always thought of it as a bit of an anti-depressant feel I I don't consider myself somebody who's depressed but I can get a little low level malaise if I'm staying up till 11:30 12 and even waking up at 7:00 I don't feel quite right and when I go to bed early and wake up early I feel really really good

you do all day long and what's interesting about that is it works both ways so that malaise that you're speaking about also happens for evening types who are forced to be M types unsympathetic no I'm kidding just kid just just kidding I mean Society is we are desperately biased towards the the morning types and we chastise and stigmatize evening types as being slothful or lazy that they just can't get it together why can't you be at the gym you know at 6:00 a.m. and in the office by 9:30 what's wrong 7:30 what's wrong with you

I'm chuckling because I was weaned in Academia and the late Ben Baris who was my postto adviser and then later a uh a colleague that unfortunately he passed away in uh 2017 but he used to say I don't do mornings now he was our department chair at the time but he would just say I don't do mornings but he would come in around 11: a.m. or noon but he would stay until 3: in the morning I feel like there's been a a cultural shift I feel like um 10 years ago if you were the person

who stayed late at the office or the lab you were considered a hard worker right but getting in early at that time it seems was not as rewarded nowadays maybe something's just changed in my world but I feel like the um the person who gets in first kind of gets the prize in terms of the the um psychological credential yeah I think there is there is that um reward bias that's given it's this notion you know the early bird catches the worm so I think the we we're desperately unkind Society is engineered towards morning types

it's engineered against evening types the reason that that's not fair is that this and I'll come back to timing again and and how it works and why it's important and the fourth ingredient the fourth macro but coming to chronotype the reason it's unfair is that it's not your fault that your chronotype is largely genetically dictated and we Now understand that there are at least 22 different genes which augment your chronotype which determine your chronotype in other words it is gifted to you at Birth it's hardwired and it is not your fault yet we still have

this stigma and this this I think disgraceful you know not only under appreciation but almost this kind of Ry look evening types are of a certain kind not very favorably viewed so think about it this way you would never let's think about another trait um eye color that is you know genetically determined and you were to look at me and you would say ah he's got blue eyes you know um it's just you're kind of lazy because you've got blue eyes oh you've got green eyes gosh that's wonderful that's well done congratulations wait a second

it's not I I didn't get the choice it's genetic was the same with your chronotype but coming back to why me I included it in this sort of algorithm of what is good sleep if I were to take a an extreme morning type and force them to stay awake until midnight they're going to be incredibly tired they're going to be so tired and they're going to be grumpy and miserable and they will have no problem falling asleep the problem however is that they're still going to because of their C their natural chronotype which in which

determines your Cadian Rhythm so everyone has this 24-hour circadian rhythm as you know you've been a wonderful proponent of that and done incredible work in this area we all have this 24-hour Rhythm and it looks like a sinusoidal wave it sort of goes up and we as a dial species were active and awake during the day and then you get this awesome downswing at night and we're inactive at night and it steps and repeats it's just 24 4our cycle everyone has that so what's why doesn't everyone fit the same chronotype timing model of sleep if

we all have a 24-hour clock well what's different is that where that Peak and that trough sit on the 24-hour clock face varies from one individual to the next and that is what we call chronotype so this comes back to why it's important the morning type they are in their all their awesome Downs swing of the Cadian Rhythm at midnight and they are miserable they're desperate for sleep and when you put them into bed at midnight 4 hours later than they would otherwise they are gone the problem is their Cadian Rhythm now starts to climb

back up around 4:30 in the morning and even though they went to bed at midnight they're probably going to wake up artificially before the 8 hour or 7 to9 hour completion and they're going to be short slept on the back end of sleep this happens to me many many times I want to go to bed around 8:30 or 9 but for social or work reasons I stay up until 11:30 or 12 I fall asleep very easily yep almost always have fallen asleep easily and then 3:34 in the morning I'm awake and you cannot get it's

almost as though you tell I tend to do this yoga NRA non-sleep deep rest and sometimes I can fall back asleep that way but often times it's a struggle and so I've been and it's a struggle because of your chronotype and your Cadian Rhythm which is on its wonderful piston upswing now apologies for the Motorsport reference but I obsessed yeah I can't help myself I'm sorry Matt's a big F1 fan folks just as is Peter AA so anyway the awesome upswing that you're experiencing for your Cadian Rhythm prevents you from sleeping in further but now

let's reverse the table let's take the evening type and I put them into bed at 900 p.m. or 10 p.m. when normally they will not be ready for sleep until 1 a.m. and they're lying in bed and they are wide awake and they cannot fall asleep and this is the principal reason that I will get evening types coming to me and they'll say look I think I've got terrible insomnia I just have and there are you know you can think about insomnia in lots of different ways but there may be two broad categories one is

that you have sleep onset insomnia I can't fall asleep well the second is I have sleep maintenance insomnia which is the sort of the thing that you were describing which is where and you don't have I don't think you have insomnia but I'm just as an example you fall asleep quickly but you can't stay asleep that's the maintenance insomnia so they will come to me with the opposite of your concern which just they say I just cannot fall asleep and I say okay let me just ask you a few questions and we go through the

chronotype questionnaire and it's very clear that they are an evening type and you know there's lots of different things that you would want to exclude to make sure they don't have insomnia and then you can say you actually don't have insomnia you you're just an evening type and you're going to bed at the wrong moment in time and if you to try to go to bed at midnight you're not going to suffer from the problems that you have and you'll sleep through later but of course their response is well I need to be in work

by you know 8:00 a.m. and I've got an hour commute so I have to be awake at 6:30 so I need to be in bed by 10 so on both of these ends you can see that the morning type who goes to bed too late falls asleep easily but can't stay asleep the evening type who is forced to go to bed too early they can't fall asleep but then they stay asleep and when the alarm goes off at 6:30 a.m. they don't want to wake up so this is why when you sleep out of synchrony

with your chronotype things do not look good so in those two circumstances let's say that I standardize it everyone is going to go to bed at 1 p.m. and wake up at 6:00 a.m. and let's say that we've got a a morning type not an extreme morning type who kind of likes to go to bed around 9:45 they are going to sleep very well it's very close to the Natural Rhythm so and then I get an extreme even in type who likes to go to bed at 2: a.m. and I have them sleep the same

opportunity amount 8 hours at the very same time well surely they should be identical they're not going to be it's not that they don't have the same opportunity they do eight hours it's just that one is placed at the inappropriate time on the 24-hour clock for the evening type but appropriately for the morning type and thus the quality of sleep that they each have is very different and that's why you always need to build into a metric of what is good sleep it's not just about quantity or quality or getting it regular it's also about

where do you place your sleep opportunity window on that 24-hour clock face to align with your chronotype when you fight biology you normally lose and the way you know you've lost is disease and sickness that's why to me that final te of qqr t is so critical does that sort of unpack and explain this this beautifully yes beautifully and as you were finishing up there I was thinking that um first of all we've heard of Corona types or many of us have but I the way you described it is um makes it extremely clear as

to why this almost has to be the case because if we think about the extreme example of mistimed sleep which is shift work you know being awake at night and sleeping during the day you know essentially nobody has that chronotype yeah um but people force it upon themselves and by the way thank you shift workers we need you um you know if I have an appendicitis at 4:00 a.m. in the morning I'm very grateful for people who can help save my life right truckers Airline employees and on and on um nurses Etc parents taking care

of kids in the middle of the night that shift work but we know that there are health issues associated with being nocturnal and sleep injuring the day um but of course there are a bunch of other variables like lack of a avability of sunlight if you're sleeping during the day and you're um and you're awake at night but I realized there's no reason to think that one can slide their sleep timing um around even by a few hours and still get away with it in other words this notion of chronotypes makes perfect sense it's just

that the shift work is the most extreme example of being out of sync with with your with your chronotype so I'm certainly going to take this chronotype test but I'll tell you right now if I could get to sleep tonight at at 9: and wake up at 4: that would I that feel so good I'm going to put you in my car I'm going to do an intervention you are going to be in bed by 9:00 this evening non-negotiable fair enough this is um yeah well so we have q qrt right quantity quality regularity and

timing how do we know if we're getting enough sleep and you know uh this is something that you know you say 7 to n hours um I've heard well if you're feeling alert during the day but perhaps have just a little bit of that postp perenial dip is it I get that right um then you're probably okay but presumably there's some other ways to to gauge whether or not we're getting enough sleep or not so there are certainly some ways that we do it in science and clinically but let's let's let those go for a

second and just say for people listening what are some very easy tests I think the first test that I would offer is if you if your alarm clock didn't go off tomorrow morning would you sleep past your alarm clock and if the answer is yes which for many people it will be then you're not getting enough sleep you know no other species as well by the way artificially terminates their sleep it's so interesting but we humans will do it we'll wrench ourselves out of sleep now I told you that regularity is key and I do

have an alarm clock I usually wake up close to it or a little bit before for it so I do Advocate an alarm clock in fact I would argue that you should have two alarm clocks you should have a toed alarm clock and to wake alarm clock you we only most of us only use an alarm clock in the morning why don't we have it to tell us when it's time to go to bed so I have both of those so I would say that it's it's good to use to keep yourself regular but truly

if you would sleep past that alarm time then you're probably not you're not done with sleep your body isn't done with sleep and animals would not would never do that and so I think that's the first metric another metric sometimes it's not that incredibly specific but have you ever been driving day after day after day and sometimes you think I don't know if that light was red or green that I just went through inattentiveness your driving man um bite your tongue Walker bite your tongue so that was you may have been that's that's one you

know potential concern in fact one of the ways that we've developed a metric for dose response to sleep deprivation is using concentration and alertness tests so in other words if there is a breathalyzer for a lack of sleep doing these concentration Focus concentration tests is they are so sensitive they're so predictive you get people just to focus on a screen and start to do very basic stimulus response and they can do that for the first minute two with stimulus response um for those that don't know might be uh uh three letters pop up on a

screen and then you're you you pick uh two keys uh you you have access to two keys on a keyboard um if the if there're two letters that are similar you press right right key if there there's only one there aren't two or more layers that are similar you press left key simple simple things but we have to pay attention to a rule that's right you're just doing a lot of different um uh Trials of different rules and it just becomes monotonous it's not really very challenging you have P ATT and that perfectly mimics in

some ways but we don't do it for two or three minutes we'll have you do it for 10 minutes and my goodness is it mind numbing I mean it's kind of just but it mimics very well think about you know just even a 1hour road trip at 10:00 in the evening and you're on the way the freeway all you've got to do is just focus on the road and the white lies are coming and there's nothing much to do and you've got to attend and focus not for 10 minutes but for 60 minutes when you

are underslept one of the dangerous the big problems with a lack of sleep is that you don't know you are sleep deprived when you are sleep deprived and we know this because when I'm tracking your performance object ly it's going down and down and down but when I'm asking you subjectively how do you think you're doing in terms of your performance you say I'm hanging in there so far I'm I'm good so subjectively you think you're fine but objectively you're not the analogy would be a drunk driver at a bar you know they've had seven

or eight beers they've had six shots and they pick up the car keys and they say to you look I'm fine to drive home and your response is no I know that you subjectively think you're fine to drive but trust me objectively you're not I'll just call you a taxi don't worry it's it's fine it's the same way with a lack of sleep so I make this point about going through the traffic lights because you can have these lapses of attention and these lapses of attention are caused by micro sleeps micro sleeps happen when the

brain just very briefly it's almost like one of those toy ducks that kind of dips its bill into the water and then sort of comes back up again and dips your brain just drops down and has a quick sample of sleep and micro sleep and we can measure it in your eyelid that your eyelid starts to have what's called a partial closure and it just kind of goes half the way over or it closes fully shut that's a micros sleep even when it's half open your brain is essentially offline it's in a sleep-like state we

can measure it and then it comes back online so I bring that that's a very long way of saying that's the second metric I would use are you having these absences where you just kind of lapse another is that you mentioned it before I just don't feel restored um you could say look I I sleep for probably around about 7 and 3/4 hours every night but I just don't I don't feel awake I don't feel refreshed I don't so can you operate without needing caffeine and have good grace good mood and good cognition without needing

caffeine before 11: a.m. in the morning and if the answer is no you may be self-medicating your state of insufficient sleep but that metric of saying I sleep 7 hours and 45 minutes that's what my sleep tracker says but I don't feel refreshed that comes to the second que of qqr sufficient quantity of sleep my guess is that I would then look at the quality of your sleep and we probably find a deficiency in the quality of your sleep so there are these different sort of tools that you can use but a good one is

do you feel refreshed and restored by your sleep it's not a guarantee any of these but in order to answer that question do you feel refreshed and restored by your sleep could we dig just a little bit into some of the Contour of the day so uh if I get a good night's sleep which for me means going to sleep early waking up early which tonight we are ABS that's the plan I wake up uh pretty quickly I'm alert upon wake up maybe 5 10 minutes to get out of a semi- groggy state but sometimes

I'm just eyelids open I'm ready to go um is the uh latency from wakeup time to uh full alertness is that a relevant metric the other question is whether or not um the postp perenial dip is a relevant metric uh we established already that it's natural to feel a bit of an energetic dip at somewhere in the afternoon I think you said between 1 and 4 p.m. 1 and 4 yeah yeah something like that uh for me that's true between the hours of 2: and 300 p.m. um assuming all other things equal I just experienced

that no matter what um but I could imagine some people are really dragging in the afternoon and they would like to know is that the normal postp perenial dip or is that a reflection of not getting adequate sleep is there any way that we could just dig into these two times of day as as a it's kind of a um a measure uh of evaluating one's duration and quality of sleep a little bit more beautiful questions I would say that one should not take necessarily either of those two as your best metric the reason is

the wakeup component for some people like you you're waking up and you are good to go pretty much out the gate many people however will experience something called Sleep inertia which is this it's almost this just period of time it's a bit like a sleep hangover the first hour I'm going to have to come back to a car analogy it's like a classic car engine where you don't just pull out and you can rev it and it's you know it just needs you need to warm it up gradually bring the the oil temps up and

the and at that point after about an hour you're up to operating temperature and you're good to go it's the sense of okay I walk through into the kitchen and sort of your partner maybe looks at the dishes and I say I know darling I know I said I was going to wash the dishes I I so sorry I forgot but can I just have my cup of coffee and I'll be the very best version of myself in about an hour can we discuss it then because right now I'm not the best version of myself

that's sleep inertia and that is natural for many people now if you are an evening type and you're waking up early you're going to have a much heavier sleep inertia period than you would do that is natural to you but I wouldn't necessarily use that as the the direct measure because many people will have sleep inera and if you do you may get worried if I say oh it's the very best measure that you're not getting quality of sleep the postp prial dip as you mentioned there before even you the the the Monumental um organism

called Andrew hubman even you can fall prey to that and do fall pre to so that's perfect I've actually learned to love it I just love it you know here it comes and I okay that's my circadian rhythm um we'll talk more about circadian rhythm in a few minutes but um and if I can get 10 to 15 minutes of shut eye time in that postp perenial dip then I really love it and you y and I bounce right out of that and we'll speak about how we were designed to sleep maybe in in a

later episode two and whether that should be the way human beings are sleeping so I wouldn't necessarily use that I'm I always have this post penial dip does that mean I should be be worried about sleep I would say that if you have excessive daytime sleepiness throughout the day where you're constantly tired and that is a term that we use in in sleep medicine is excessive daytime sleepiness um or EDS um that should be of a concern I would use a slightly different metric of the same question but at a different time of day let's

think about that Cadian rhythm again for most people even if you're a morning type or evening type by about 11 a.m. by about 11:00 a.m. midday you're really starting to get to your Peak you know most people are somewhere either side of the peak or around that Peak I would say that if you are feeling groggy and not alert and awake at 11 11:30 depending on your chronotype I would use that as probably the better metric of my daytime sleepiness but and by the way it's very interesting that that Peak if you look at that

c Peak when you're at your optimal it's both your optimal for your brain but it's also for your body it's the point at which your core body temperat just starts to Peak that's the moment where you have optimal physiology and when you look at world records that have been broken in the Olympics and you plot them on the basis of time of day you see this incredible beautiful Spike where most people are breaking World Records right in that Cadian sweet spot around that midday Peri period why it's because that's the period where human physiology seems

to be at its optimal thermal temperature at least it's fascinating fascinating right around sometime between 11:00 a.m. and 1 1 1 p.m. p.m. yeah depending on what time somebody goes to sleep and wakes up correct yeah and what time their chronotype is and that will very but on average because for me would be my Peak alertness and and physical ability uh work output um is somewhere between 10: a.m. and noon yeah y yeah and that fits both with your brain and my guess is that if we were to get you into the gym and have

you go through your routine and see if we could do that routine once we've got a basil metric set of metrics I will have you do it at 7 a.m. then have you do it at 9:00 a.m. then do it at midday then 3 p.m. then 6 p.m. and then 10 p.m. same workout same human being but there will be definitive periods of time in the day when you are optimal and my guess is that that optimality of brain is matched by optimality of body such that your Peak Performance output and let's say your Peak

jump height or your Peak muscle strength would be right around those time periods that fit with your own Cadian chronotype rhythmicity so you've been talking about this 24-hour oscillation in sleep wake activity called the Circadian rhythm maybe we can drill a little bit deeper into the Circadian rhythm you know what is it um what can shift it if it indeed can shift and I'm especially curious about forces other than the Circadian rhythm that have an impact on sleepiness sleep and wakefulness so the way we think about it in sleep science and there is some argument

that it's maybe even more complex than this but for the most part there are two main forces two main processes that will determine when you want to be awake and when you want to be asleep the first of those we've spoken about which is your Cadian Rhythm and that Cadian rhythm is um you have a clock inside of your brain you have a central 24-hour clock and it's a master clock and that clock as you've spoken about many times is called the supermatic nucleus we don't have to get hung up on the the statement just

think about it as your master 24-hour clock and it beats out this rhythmic sort of message of activity for us because we're dianal during the day and then inactivity at night activity during the day and it just goes up and down up and down every single day that's your Cadian Rhythm and that's the superism the reason I say it's the Master Clock we've now learned that there are these Cadian Rhythm clocks in almost all cells of the body you've got clocks all over your body in these sort of they're tiny little clocks but a little

bit like Lord of the Rings just like there's one ring to rule them all well there's one clock to rule them all and that is the central brain clock the supermatic nucleus now you can dissociate those different clocks and you can get them kind of doing some funky things but for the most part it's the central Time Giver so you would think that well that's all you need to tell your brain and your body it's time to sleep or it's time to be awake it's not there is a second force in place here and it

is called proc or we sometimes call it as process s or sleep pressure so you've got your Cadian Rhythm on the one hand going up and down every 24 hours but then you've got this funny thing called Sleep pressure sleep pressure comes down to a chemical that is called adenosine so from the moment that you and I woke up this morning and everyone listening a chemical has been building up in your brain that chemical is called adenosine and the more of it that builds up the sleepier and sleepier you will feel and after about 16

or so hours of being awake there is enough of that sleepiness chemical that adenosine um sleep pressure by the way it is a chemical pressure it's not a mechanical pressure you don't have to worry that your head's going to explode uh if you go longer than 16 hours a week but that sleep pressure is going to start weighing down you on your shoulders and you you can sense that feeling where you start to think ah it's you're watching television you you're starting to go down sort of the hill and you think I should go to

bed I'm I'm tired now that's because of one of two things that's happening firstly you're getting to that Peak Crescendo of adenosine where it's just getting so powerful that it's knocking you over and you're ready for sleep usually when you are in synchrony with all of your biology these two forces your Cadian Rhythm that goes up and down every 24 hours and your sleep pressure align in this beautiful sort of frister Ginger Rogers dance partnership and they're in harmony the strange thing is that they know nothing about each other and they don't care about each

other one does not influence the other they are completely too independent things but let me run it out in the normal circumstance and then I'll describe to you a good example of how I can separate those two and show you that they're truly independent so normally when we're in a sort of stable rhythm of sleep wake activity were awake during the day we've got this awesome upswing of orcadian rhythm and then in the evening let's just take you for example as you're getting into that sort of 8 00 p.m. region your circadian rhythm has finished

its peak many hours ago and it's now starting to descend down and you're getting onto the Steep phase of its downward sort of stroke of its awesome downward movement but also don't forget that at that moment your sleep pressure your adenosine is also now at its peak you've been awake for now almost 6 hours so the moment when your Cadian rhythm is on its nice downward swing and your highest in your levels of adenosine in your sleep pressure that's the moment truly that will determine okay now is when I feel nice and sleepy so then

what happens then you go to sleep you come down that curve of your Cadian Rhythm and you kind of hit its Nader its lowest point in the middle of your sleep phase but also when you go to sleep that second factor of sleep pressure you are your brain gets the chance to clear away that adenosine and it seems to be about a 7 to n hour period of sleep is enough time for your brain to jettison all of that adenosine that has been building up across the 16 hours of Prior wakefulness and then these two

things align beautifully again when it comes to your natural wakeup time you've been asleep for let's say 7 and 1 half hours you've cleared out all of that adenosine so you no longer have the weight of that sleepiness pushing you down but also your Cadian rhythm is now on its awesome upswing and when those two things align when you've dissipated and jettisoned all of that sleep pressure and your Cadian rhythm is starting to rise now that's the time when you would naturally wake up so that's things when they are working well and in alignment let's

say that I now take you and I'm going to deprive you of sleep for 24 hours so now coming into sort of 10 p.m. your Cadian rhythm is dropping down and your adenosine is starting to get high and by about 2 a.m. you're probably not going to be happy by about 4 a.m. or 5: a.m. you're miserable why because you've now been awake let's say for almost 20 hours straight so you've got all of this excess sleepiness adenosine pushing you down screaming at you you've been awake for 20 hours and your circadian rhythm is at

its lowest point desperately wanting to pull you into this thing called sleep and you feel terrible but then something strange happens by 11:00 in the morning relative to let's say you know four you've now been awake for many more hours still so you've built up up even more adenosine so the prediction would be that if it's just adenosine alone that makes the difference you should feel even worse at 11:00 a.m. you don't you feel better despite being awake for longer why because your Cadian Rhythm has come to the rescue and it's now starting its upswing

and it lessens the distance between those two and you feel a little bit more alert but then as I push through later into the day by about 6:00 p.m. 7:00 p.m. you're now on your Cadian down Swit once again and you've been awake for even longer and at that point there's almost nothing that can keep you awake you're going to be falling asleep on your feet and your toast but that's a nice demonstration of how you can separate those two and despite one continuing on you can start to feel better because the other has come

to your rescue and that shows me that your Cadian Rhythm doesn't care about how much adenosine is in your brain it's just going to keep going up and down up and down every 24 hours and your Denine level doesn't really care much about your Cadian Rhythm it's going to just build and build and build the longer and longer that you're awake and then get dissipated whenever it is that you sleep the clearance of adenosine uh I'm curious about it how does that work um so this chemical adenosine is building up in our brain does it

also build up in the body um it does but in the brain it has this very interesting influence now I've described it as making you sleepier and it does that's exactly what it does but it does it in a very very interesting way it's a a bidirectional way there are at least two different um adenosine receptors or adenosine welcome sites within the brain and adenosine is very clever in how it makes you sleepy adenosine as it's rising will turn down the volume on the Wake promoting regions of your brain but yet will increase the volume

on your sleep promoting regions and by way of this Jewel action that's how it seems to instigate this feeling of sleepiness by temping putting the brakes on wakefulness but hitting the accelerator pedal on sleepiness but then adenosine seems to be part or one of the reasons that it builds up is because it's a metabolic byproduct of cellular activity of cellular metabol ISM and it seems to be that the longer that we're awake because our brain is very cerebrally active during the day even though I told you that the brain state of sleep is very active

it is it's a very metabolically active state of sleep it is less metabolically active however during deep non-rem sleep and it seems to be that it's deep non-r sleep that is the principal time when we clear we get the chance to clear away adenosine now now adenosine clearance is happening all of the time it's just that the rate of accumulation when we're awake exceeds the speed with which we can naturally clear but when our brain goes into deep non-rem sleep and becomes less metabolically active it's not as though there's necessarily a more active or a

very proactive state of Deep Sleep doing that cleansing it's not it's the same process of adenosine clearance it's just that there is no longer the accumulation that's happening so it gets the chance to catch up on the days adenosine accumulation and then reduce down that adenosine debt and then get you to net net neutral by the morning in fact the amount of Deep Sleep the quality of that deep sleep that you're getting specifically the electrical quality of your deep sleep is a very good predictor of how well you dissipate that sleepiness again it's not as

though there's something special about non-rem sleep that is proactively doing the cleansing faster than happens when we're awake it's just that the rate of accumulation when we're awake is greater than the exceeding and exceeds the capacity of the clearance so it builds up when we go into non-rem less metabolically active it now the clearance exceeds the buildup and you're able to cleanse that debt I have two more questions the first is about growth hormone so I was taught that growth hormone is released primarily in sleep although there are some daytime activities that can promote the

release of growth hormone as well certain forms of exercise maybe some thermal stimula Etc but that the major event of growth hormone release occurs in sleep is that true it is although it there is some argument that it is is it sleep dependent or is it simply sleep coinciding okay meaning that is it it's that at the time of day so is it a cadium process where it's just nighttime Nur means that you release growth hormone or is it nighttime plus sleep that is needed and it seems to be a mixture of both but it

seems to be more sleep dependent than it is nighttime dependent and sleep independent I probably probably should have said before growth hormone critically important for growth of children during development but also for tissue repair and Metabolism throughout the lifespan throughout the lifespan when we're adults we critically need it right so if I understand correctly when one goes to sleep growth hormone is released but that there's a circadian component as well so it's a bit of an and gate as they say which is that you need this and that in order to get growth hormone release

and the reason I ask this uh and I'm going to frame it this way because I think it's going to both clarify what you said um and also lead to a practical uh step which is about sleep regularity and timing I've heard that the growth hormone surge is greatest at the beginning of the night of sleep and that if we go to sleep a few hours later than usual we miss the opportunity to experience the same level of growth hormone release even if we sleep the same total number of hours right so um yet more

incentive for uh regular sleep timing yes so you're right it's an and gate so it's night ESS does help but sleep helps perhaps significantly more meaning that I can have you experience the nighttime but I can deprive you of sleep and selectively of deep non-rem sleep and I can markedly imper your growth growth hormone release but differently I think it tell me if this is correct but differently if somebody has to work the night shift and they sleep during the day they'll still get a growth homeone release but not as much growth hormone release were

they to have slept at night correct so we can do it one of two ways so my way is to say I keep you on a dial nocturnal sort of schedule where you're awake during the day and you asleep at night but I'm going to selectively deprive you of just your deep sleep at night so you're still sleeping and you're still spending the night ESS in bed which is not the shift work version but I can block or not block I can reduce significantly reduce your growth hormone because I selectively deprived you of sleep or

I can do the opposite which is the shift work approach which is I'm not going to deprive you of sleep you're going to sleep during the day but now I have held sleep constant so in my version I have held night ESS constant and I've manipulated sleep in your version the shift worker we've done the opposite we've held sleep constant they're sleeping during the day but we've manipulated nighttime Ness and now as you said yes they will release some growth hormone even though that's not the natural time on the 24-hour clock when we would see

growth hormone released why because they are getting sleep because it's a somewhat sleep dependent process but they're not going to necessarily release as much in part because they're not experiencing sleep at nighttime phases so you can you can elegantly separate those two out and that's why it's not quite one or the other but it seems to be both certainly it's sleep sensit I would say sleep sensitive is a very good way of describing it okay so translated to uh actionable protocol everyone should strive to get uh sleep ideally at night um of sufficient quality and

quantity which you already discussed and getting sufficient amounts of deep sleep is going to be especially important for sake of growth hormone release correct got it my my last question has to do with the other end of the Sleep Cycle which is toward morning and waking which is the hormone cortisol we hear so often these days about cortisol and people often frame it as bad cortisol is bad you hear this that is simply not true remove cortisol from an organism they don't they will not do well right and um we need cortisol uh for immune

system function for waking for certain forms of memory formation although too much cortisol is a Bad Thing indeed not enough cortisol is an equally bad thing indeed so um what is the relationship between cortisol and emerging from sleep and put differently what is the relationship between deep sleep and cortisol meaning is sleep one way that we keep cortisol at Bay during stages of the 24-hour cycle when it would be delerious to have elevated cortisol yes it is and that's one of I spoke about and we'll come on to this perhaps in when we speak about

emotional and mental health and when we are underslept we shift over into a more sort of activated sympathetic you know agitated state of our nervous system that's that's one aspect of it but there's another aspect of the stress response which is yes you get elevated heart rate you're more sympathetic which is this activated State rather than parasympathetic but you also get when you're sleep deprived a greater release of the stress hormonal axis which is called the HPA axis which if you really want to go to detail it's the hypothal pituitary adrenal axis which is a

fancy way of saying that it's a signal from your brain going down to release cortisol so when you go into deep sleep not only do you shift over into the nice quiet rested quiescent state of the nervous system but you also get a dissipation in that stress related axis and the relief of cortisol cortisol however seems to be also under the strict control of your Cadian Rhythm where it drops down at night and in fact you have one of the the steepest declines right at the moment when you're starting to get sleepy too almost as

though your brain and your body know we can't have cortisol even at sort of normative levels that you would have during the day because otherwise this person is just going to still be a little bit too wired M this is the problem with a stressful event after say 8:00 p.m. at night if you see see something stressful experience something stressful I mean that um if it's stressful enough will spike your cortisol at that late hour can really impede your entire sleep structure it's a I would say it's one of the things that I would advocate

in terms of a good sleep optimized routine and we can come on to that and avoiding stress and arguments and TR and disturbing news and things like that as much as as possible yeah um in the late evening and and early night hours even if you don't think you're necessarily someone who's sensitive to that now it turns out I am someone who is sensitive to that it can really quite trigger me so I stay away from it we often see this with insomnia too and we call it the tired but wide phenomenon and people will

say to me look I am just so tired man I am so so tired but I'm just so wired that I can't fall asleep I'm desperate for sleep I know I want sleep but I can't fall asleep cuz I'm just so wide and that is a sympathetic hyper cortisol State and we you can see it in their physiology but coming back to your question cortisol will drop naturally throughout the night but then it starts to rise back up and will start to produce its fantastic sort of peak climbing rate right at the moment when you

would naturally again want to wake up so what we we're mapping here is this wonderful tapestry this Kaleidoscope of coordinated biology that your adenosine levels are finally coming to their lowest point your circadian rhythm is starting to rise your cortisol levels are starting to rise your core body temperature is starting to increase because it's dropped throughout the night all of these things unite in this beneficial timing ballet of just brilliant that naturally has you waking up and feeling like you're ready to go if everything is aligned if you've got your chronotype right your sleep quantity

your quality regularity and your sleeping you know in appropriate sort of timed amounts well your enchantment with sleep is indeed infectious uh I've experienced it and I know that everyone listening and watching has experienced it as well as you've taken us through this truly spectacular Voyage through this phenomenon that we call sleep I mean you informed us about what sleep is what the different sleep cycles are uh how they are structured and interrelated uh you talked to us about the four macronutrients of good sleep quantity quality regularity and timing it's highly actionable information and then

of course some of the hormonal neurochemical uh interactions and consequences of good sleep bad sleep for mental health physical health and performance so first I'd like to just extend a giant thank you for taking us on this Voyage in this first of several or more episodes uh of this miniseries on sleep and I very much look forward to our discussion in the next episode about how to improve one's sleep and perhaps even optimize one's sleep so thank you Matt ever so much on be behalf of myself and listening audience can't wait to continue the discussion

further can't wait thank you again for having me in this opportunity um what you do for the public by the way in terms of your advocacy for Science and also for health for what you do thank you and for giving me this opportunity to be here to share the message of sleep thank you thank you so much for the kind words um it's a labor of love and it's a it's a delight to be able to join arms in educating with you thank you thank you for joining me for today's episode with Dr Matthew Walker

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