GUEST SERIES | Dr. Matt Walker: How to Structure Your Sleep, Use Naps & Time Caffeine

Welcome to the Huberman 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 ophthalmology at Stanford School of Medicine. Today, March the 3rd episode in our 6th episode series all about sleep, with expert guest Dr. Matthew Walker. During today's episode, we discuss how to structure your sleep

for optimal mental health, physical health and performance. We discuss monophysics sleep schedules, which are the more typical sleep schedule where you go to sleep at night and then wake up in the morning, so sleeping in one bout as opposed to polyphasic sleep schedules, which are when you sleep in two or more bout, either at night or perhaps a shorter bout

of sleep at night and another bout of sleep during the day. We also discuss naps, including how to nap, how long your nap should be, whether or not naps are good or bad, in particular whether or not they're good or bad for you. It turns out there's varies according to individual. We also discuss how your needs for sleep and naps vary across the lifespan.

And we discuss body position during sleep, which might seem excessively detailed, but it turns out that body position during sleep is critical for ensuring that the sleep you get is optimally restorative. As with the first two episodes of the 6th episode series, today's 3rd episode is filled with both science that is the biology of sleep and napping and body position and how those relate to one another, as well as practical tools that

you can use to vastly improve your sleep. 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 BetterHelp. BetterHelp offers professional

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for many people, it's as beneficial as getting regular physical exercise. The great thing about BetterHelp is that it makes it very easy to find a therapist that's optimal for your needs. And I think it's fair to say that we can define a great therapist as somebody with whom you have excellent rapport, somebody with whom you can talk about a variety of

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Today's episode is also brought to us by waking up. Waking up is a meditation app that has hundreds of different meditations as well as scripts for yoga, knee, and non-sleep rest or NSDR protocols. By now, there's an abundance of data showing that even short daily meditations can greatly improve our mood, reduce anxiety, improve our ability to focus,

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And now for my conversation with Dr. Matthew Walker. Dr. Walker, welcome back. Dr. huberman, an absolute pleasure. Let's talk about the different types of sleep, because I think most people think of sleep as just one thing. Most people sleep at night, some people also nap, a topic we'll also discuss today, but turns out there are a lot of different

types of sleep. What are the different types of sleep? And what do they do for us? And I guess everyone's probably wondering already, I certainly am, what types of sleep are we already engaging in? Meaning am I involved in or having multiple types of sleep each night? This is a fascinating question. And it comes back to something we've discussed in a previous episode. The different stages of sleep and how they unfold, we've described that fascinating

stuff. What you're already asking, though, is an incredibly sort of subtle but relevant question. How should I be sleeping in terms of the phases of sleep? Should I have one phase? Should I have two phases of sleep? Or should I have many phases of sleep? In some ways, you can answer that question on the basis of the lifespan, because how it is that we sleep in terms of those chunking sessions changes as we develop. To be clear in the

main culture, I'm saying monophysic, biphysic, polyphysic, unpack that. Monophysic obviously just simply means a single phase, monophysic. And when you say phase, you mean one bout of sleep. Correct. So that would be within a 24 hour period, you are having a single bout of sleep. Biphysic then means that within that 24 hour phase, you are having two bout of sleep. And we'll speak about how those bouts are split up. Are they split up between

two halves in the middle of the night? Or are they split up in terms of longer at night and siesta like nap in the afternoon? And then we can speak about polyphysic sleep. Polyphysic sleep, we in sleep science have been using for many years in the context of infancy, because there is any new parents will know. Infants do not just simply have a nice single bout of sleep. They're up, they're down, they're up, they're down. And they have many bouts of sleep

within that 24 hour period and that's polyphysic sleep. The other term or the other application of that polyphysic sleep has been used more so in the sort of interesting biohacker movement and we can we'll come back to that perhaps later on. So how do these different phases of sleep change across the lifespan? Well, we've already said that when you're an infant and you're first born within the first year of life, you are incredibly polyphysic and

you are probably going through wake sleep phases every two hours. Why do you do that? I can't you just simply be born and sleep in a monophysic way. It's for at least two reasons. First an infant needs to feed every two hours. So their energy needs and their food intake requirements dictate that you can't sleep for very long because you need to be awake to

feed and then you go back to sleep. Within probably the first six months, things will start to change a little bit but the second reason that you are highly polyphysic when you are first born is because you're super chiasmatic nucleus and in another episode we spoke about the central master 24 hour clock that beats out your circadian rhythm, the rise and the fall, the wake and the sleep. That has not yet developed. It hasn't been glued

into place into the brain. There's 24 hour clock. So the infant seemingly knows nothing about when it's light or when it's dark outside. They're just awake your sleep. So that's the second reason. Energy feeding needs is the first and then an absence of yet a fully developed 24 hour clock in the brain to beat out that beautiful dictated rhythm. By about age one, that number of phases of sleep are starting to decrease but it's still highly

polyphysic. It's not until you get to probably age two or three that now you're starting to see this consolidation of sleep. What do I mean by that? Sleep is now happening more dominantly in the night phase of the 24 hour cycle and there are a few abouts of sleep during the daytime. Then perhaps by the time you're in kindergarten, you may be down to just two sleeps. So now we've switched from polyphysic sleep as infants to byphysic sleep

as kindergarten. Could you describe that as byphysic patterns? I recall in kindergarten having nap time in the afternoon. Put out these little mats and every kid would just go like, it actually sounds really nice. And we'll speak about how some adults do this too. But almost every kindergarten system that I've inquired about around the world's different nations, they all have this nap time. And any teacher will tell you if one of

those children does not nap during that period of time, they are the loose cannon. They are the live wire. And in subsequent episodes, we'll speak about exactly how sleep harnesses and improves our emotional and mental health and how it falls apart when we don't. So that's how it certainly is emerging biologically. And that's how we as a society respect that

and accommodate that. And then probably by the age of starting school, sort of five or six, now we're starting to see fully monophysic sleep, children sleeping, long bouts at night and then being able to sustain wakefulness during the day. At that point, you have locked in your monophysic pattern and that will continue throughout adulthood and into old age with a few caveats that we'll speak about. So that's how sleep unfolds in the monophysic,

bifasic, polyphysic sleep across the lifespan. It doesn't quite tell you however, how those different stages of sleep change across the lifespan. So I've shown you the view of sleep across the lifespan through one lens of the microscope. If we click down one lens and focus more deeply on the different stages of sleep, there we see a fascinating story. In utero, for the most part, you are in a sleep like state as a fetus once you get to a

certain point of development. In utero, that sleep like state seems to be more so something that looks like REM sleep. Now it's not fully fledged full fat REM sleep yet, but it seems to be something very much like REM sleep. I say this because in the first episode, I told you as we go into REM sleep and we start to, as adults, dream, the brain paralyzes the body so that the mind can dream safely. Those kicks and those punches and those elbows

that a mother will feel from the fetus seem to be during this dream state often. And I don't want to shatter any illusions of you start singing or you're cuing and you get these bumps and these elbows and these legs kicking in is beautiful. It is beautiful. But it turns out that it's probably the REM sleep state, but the muscle sort of paralysis

has not yet developed. So you're getting these electrical bursts, this frenetic activity of REM sleep that we described, but you're not getting any of the blockade of the motor output. And so it expresses itself as these kicks and these bumps. And then during the first six months of life, and at that point in the first six months, it was infants are sleeping anywhere between 14 to 17 hours a day. It's immense, isn't

it? I mean, it's right up there. If you look across the, across phylogeny and you ask, which is by the way, a fascinating topic at some point we should do a separate podcast on sleep across different species because I know like me, you love, you know, the whole variety of species. But you've got elephants who will sleep as little as four hours and then you've got the little brown bat who is the rock star of sleep. And it will sleep

almost 17 to 18 hours a day. It nudges out the sloth in that sense. Can I ask you a question about that little brown bat? Yeah. Does it sleep hanging upside down? It does. So it can't have sleep paralysis in its little cloth. So it will not have that paralysis, but it goes through the stages of sleep very quickly. And this happens with birds as well. So birds that flock on a branch, they will sleep. And they sleep in some fascinating

ways, sometimes with one half of the brain, sometimes with both halves. But then you say, well, if I'm on a branch and there's this wonderful force called gravity underneath me, and I go into REM sleep and I have that muscle paralysis, which they do. How does that work? Well, they only have very brief REM sleep periods that last just for a few seconds. And then they regain their muscle town. It couldn't help but ask it. It's genius.

This is Laura and the fauna. Oh, I love it. But especially the fauna enchants me that much. So I don't want to draw us off course. But now we know that they can, that's why the bats don't fall. That's why the birds don't fall. Correct. So when you are then as an infant sleeping 14 to 17 hours, what's happening with those different stages of sleep, non-REM and REM? At that point, we can't really define and separate the different stages of non-REM because it's not yet fully formed. But we have

what looks like a REM sleep active sleep and a deep non-REM sleep passive state. Almost 50% of the time that an infant and newborn is asleep is spent in REM sleep. Why do I say that with some kind of wonder in my voice? Because as adults, we're perhaps down to maybe 20% of our time spent asleep is in REM sleep. But 50% of the time when an infant is asleep, they are in REM. Why would this be the case? And across all species that have REM and non-REM,

the time when we see REM sleep in highest volume amount is always after birth. There is something special about REM sleep in its function during that early period. And we now start to understand why. When you are first born, you are still going through a huge amount of brain maturation. And the recipe for the day, like when we are teenagers, is exploding the brain with synapses, all of these connections throughout the brain. What we've discovered is that REM sleep acts as an electrical

fertilizer to stimulate the growth of these connections within the brain. It's almost as though you could think about an internet service provider with this huge new neighborhood. And the first call of business is to go in and wire up each one of those homes with these fiber optic cables. That's what REM sleep is doing. And if you start to deprive, and these were studies, gosh, many years ago, by Howard Roth, Morgan, others, if you deprive animals of REM sleep, you stunt the developmental

growth of the brain. And presumably the whole animal. And the, yeah, as a consequence, I mean, if you look at its social behavior, even just that, it's profoundly abnormal because you don't have that REM sleep developed brain. I mentioned this not because there is any causal evidence, but we have seen REM sleep impermanence in certain developmental disorders, such as autism,

as well as ADHD. I don't think there is any supportive evidence yet to come out with a claim that part of the trajectory underlying those conditions is abnormalities of REM sleep, but it's a very active area of research. So it's a fascinating time there, during infancy, when you get these huge amounts of REM sleep. Why? Because of what we call synaptogenesis, which is simply the creation

of synapsis genesis. Then as you move from six months across the next 18 months, something odd happens, total sleep time starts to decrease, REM sleep starts to decrease, but non-rem sleep actually increases, even though total sleep time is decreasing. And there's a strange peak in lighter stage non-rem, what we call stage two non-rem, and those sleep spindles that I was describing

in the first episode, these burst of electrical activity. We will speak about the role of those sleep spindles in improving motor skill learning, and we've done many, many years of work in this area. Why is that relevant to this phase of life? That's right around the time when infants start to coordinate their limbs in a skilled way and begin to walk. And we believe that it is part of the

process of the development of the motor system enabling walking to begin. Amazing. So then things will change further, sleep time continues to decrease, and by about age five or six, now the cocktail blend of non-rem and REM is down to a stable ratio that will remain throughout the lifespan, which is a four to one ratio. So about 20% of the time that you're asleep will be REM sleep, and the remaining time will be 80% of the time will be non-rem sleep.

Provided one is getting sufficient total amounts of sleep. Correct. And getting it at the right moments in time that we described in the first episode, getting that appropriate cronotype match to the 24 hour clock, that will certainly alter those things too. So that's how sleep unfolds both at the first level of the lens, monophasic by phasic polyphasic, and then double-clicking how the different stages of sleep unfold and what the reasons are behind that. I then said once we're adults,

we become monophasic. Yes, to a degree, but there is some contention about the way that we sleep in modernity, that we may not be sleeping in the way that we were designed to sleep, which brings us back to by phasic sleep. In the first episode, we spoke about this strange afternoon dip in our alertness that happens called the post-prandial dip. And it happens somewhere between the 1 to 4 pm region, and it's measurable, and it seems to be biologically wired into us.

If you look at certain cultures that are not touched by modernity, so we know this have studied hunt together at tribes, they don't quite sleep the way that we do, and they don't sleep the way that we do for at least two reasons. The first is that they will often have a siesta-like pattern of behaviour, where especially in the hot dry season, they will take a nap in the afternoon.

In the wet, cooler season, that may not be the case, but they certainly have more of a bifasic pattern where they'll sleep longer at night and then have a short nap, siesta-like. And then of course, there are Latin and Mediterranean cultures, and they have this practice of the siesta-like behaviour. Coming back to the hunt together at tribes, the way that they also do not sleep in a similar manner to that which we do is they're timing of sleep. They don't go to

sleep as the sun goes down. They will usually, on average, as a group, they will usually go to sleep about two hours after sun down, and then they will wake up not with the rising of the sun. They wake up just before that, and you think, how are they predictive of the light? No. The thing that changes first before the sun truly rises is temperature, and temperature is a very strong predictor that forces them away. So when you think about how they're sleeping then, consider the term midnight.

Most of us never really think about what the term means. Midnight refers to the fact that it is the middle of the night. But for most of us in the modern world, that's the time when we're thinking about sending our last email or posting to social media. Midnight is no longer midnight for society, but it is for them. So should we be thinking about midnight as the middle of the night in the context of the extremely person, morning person who, you know, presumably likes to go to bed

around 8 p.m. Wake up around 4 a.m. Most people hear 4 a.m. and they go, oh goodness. You know, that's early. Sort of like the mighty Jockel Willink is famous for posting images of his digital watch. Usually I think it's 4 30 a.m. Wake up, and that's when he starts his workout. So his Twitter, I guess they call X now feed, and Instagram is a replete with images of his watch, 4 30, and people think goodness, that's early. But he was a guest on this podcast, spoken

to him before, but he goes to bed pretty early. That's right. Most nights. So in some sense, you know, midnight for him or for somebody with a similar schedule is truly middle of the night. That's right. But for the other chronotypes, for people that prefer to go to sleep or who naturally get sleepy around 10 or 11 p.m. or even later, how should they think about this by-phasic, polyphasic business? Because at some level we all have to reconcile our sleep schedule with

the demands of work and family and so on. That's right. So I was very specific when I said the hunt together at tribes on average, that's the way that they will sleep. But like the rest of society, there's a huge distribution, and there will be some proportion of them who are a little bit like Jocco who will be on the early side of that, on the very early side of that. But then there are other people who are clear night owls, and they may not be going to bed until, you know,

10 or 11 and waking up later. So there is a distribution there. You don't have to worry that my statement of midnight, on average, that does seem to be when we are dislocated from all of the trappings of modernity, how a group of representative humans on average will sleep. But there is huge, as I said, differences from one individual to the next. By the way, you can ask the question, why do we have these things called chronotypes? Why is there such variability in how people have

a preference for when they sleep? Wouldn't it just be easier if biology designed us all to be a sleep at the same time? Not so. We mentioned in the first episode that sleep is truly idiotic in the sense that, you know, you're not protecting yourself or the people that you care about. And if everyone slept at the same moment in time, you as a collective and as an individual would

be vulnerable for an eight-hour period, seven to nine-hour period. But by way of this wonderful injection of variability as to preferences for when people sleep, maybe there are some people who are going to bed at 8 p.m. And there are other people and they're waking up at 4 a.m. There are other people who go to bed at midnight and wake up at 8 a.m. So then think about that. At some point, what you've done is that there will always be someone or a collection of people awake until midnight,

and then will always be a collection of people who are awake starting at 4 a.m. So as an individual, everyone gets their eight-hour opportunity. But as a collective, as a clan, you've reduced your vulnerability down by 50 percent because Mother Nature injected the variability by way of genetics of chronotype to distribute that and lessen the burden. Does that make any sense? It does. And it reminds me of how the circadian rhythm, which we discussed in episode one, is about 24 hours,

not exactly 24 hours. The rhythm of the superchismatic nucleus neurons that generate the circadian rhythm, as I recall, is rarely exactly 24 hours. It's 24.2 or 24.4. And the idea in mind, the Jesso's story, is that that variation allows for entrainment matching to the outside like dark cycle, which changes across the year. So you don't want it to rigidly 24 hours, because if there's any variation in light dark, which of course there is, even at the equator across the year,

there's subtle variations, but certainly as you move away from the equator. And so these variations in your circadian rhythm clock SCN, superchismatic nucleus might be 24.2. Mine might be 24.6, 24 someone else 24.1. And in that sense, allows some maliability to to matching the circadian rhythm to outside like dark rhythms. Is that a decent

parallel for what we're talking about here? It is a beautiful demonstration that there is always some, it's almost wiggle room in how biology is programmed, because some degree of sort of noise, almost stochastic noise, can be very beneficial. And it's much more predictive of the way in which the world works. And it's much more adaptive for a species to enact and to embrace that kind of variability. And Jesso's a beautiful example that it's about 24 hours,

but it's certainly responsive to changes in light duration across the year. And it has to be because we need to buckle ourselves to the light dark cycle for optimal survival. And here's another demonstration of where it's not about the circadian rhythm, but it's about the chronotype distribution, not within an individual across the year, but across individuals at any one moment in time. And that variability once again provides a biological benefit. In the first episode, and again,

now you're discussing chronotypes. And one one thing that I've been meaning to ask is you said that chronotype is genetically determined, but that that necessarily mean it is directly inherited from mom and or dad, meaning if your parents are both extreme early morning types, will you grow up to be an extreme early morning type? You already established that during infancy and development, adolescence, et cetera, that our chronotype is somewhat massed by some of the

developmental necessities. But once we reach young adulthood and our chronotype has been established, can we look to our parents to determine whether or not we are more likely to be a morning person or a late shifted? It's very unlikely to find anyone whose parents were both extreme morning types, who is a neutral or an evening type and vice versa. So my guess is that people with, if they know of their biological parents and they know of their rhythms, it's highly likely that you will,

at some point acquiesce in your lifetime to being very similar to them. Now, there are certain life conditions and contexts where you can fight that if you're really, if you're someone who is in Kongrock band and you're touring all the time, even though your mom and dad may be morning types, and you may be a morning type, you're on the road, you're playing gigs, there's no chance. But at some point, let's say you retire and you give yourself the opportunity to express your natural rhythm,

you will go back to that. So yes, it's highly genetic. It's not entirely genetic. There is some degree of modification that happens on the basis of context. And I've just given you a good example of context. And also your exposure to light, you can be someone who is, let's say, a neutral like me.

But if you're constantly invaded by electric light at night, you're drinking too much caffeine and you're on your laptop and your computer and your phone and you're always activated by social media, it's very easy for someone like me to drift and become a one AM to, you know, nine AM person. That's not my natural type. But context and the environment have shifted me. But for the most part, yes, to your question. I'd like to take a brief break and acknowledge our sponsor,

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Again, that's drinkag1.com slash Huberman. Okay, so getting back to these different phase opportunities for sleep. Clearly, I'm getting the language wrong here. But I'm not a living actor. Monophasic, biphasic and polyphasic. Give us a few more examples of different types of biphasic and polyphasic sleep. So coming back to biphasic sleep, I described one version once we are adults, which is the CES to like notion one long bout at night,

short about during the day. And that about during the day is usually matching that drop in alertness that we described. It sort of hits that sweet spot right there. And it's quite easy for some people to fall asleep in a period between somewhere between one and one to four. Yeah. And I know it's a large window, but that just allows us to sort of know, okay, if you're someone like yourself who's a morning type, you would probably start to want to nap a little bit earlier if you were biphasic.

Someone like me and neutral, probably an hour and a half, two hours later still. But there is a different version of biphasic sleep for adults that has been described in the literature. And it's fascinating, but I don't think it's biological. It's the notion that some people will have heard called first sleep, second sleep. And now you are splitting your sleep into two phases. But there's split across the night. So the idea is that you fall asleep and you'll maybe have

four-ish hours. And then you wake up and you then are awake for several hours. And then you go back to sleep for another three or four hours. If you look in history in the record of human history, it's very clear that there were some cultures doing this, particularly if you look at some of the European cultures, Great Britain in particular, there is good evidence that somewhere between about the 15th to 19th century seems to have ended during the kind of Dickensian era.

People were describing this behavior and they would wake up in the middle of the night after about four hours. They would make food, they would play music, they would write, they would make love. It was a real thing. And I'm not suggesting that it did not happen. It clearly did. And there's a great book that outlines this. But is it the way that we were designed to sleep bi-phasically versus the CES to like? And I don't think it is. There is no good collection of evidence.

If you look at the biology of our human rhythms, that argues that there is this magical period of a huge spike in oscating rhythm that happens right in the middle of the night that should force us awake. There is one paper that's often cited for this. And in truth, that paper, if you read it, says nothing about first sleep, second sleep, doesn't speak about bi-phasic sleep at all. And that paper, I think, is unfairly used as a justification of first sleep and second sleep.

And the paper, to me, has at least three problems. It's a great paper. There's no problem with the paper and its hypothesis. But its use is justification for first sleep. Secondly, past three problems. The first is the artificial nature of the study. They weren't designing it to test the hypothesis, but they had individuals in bed for 14 hours straight relative to a standard eight-hour period. And sure enough, what they found was that when you force people night after night

to be in bed for 14 hours, somewhere after about six or seven hours, they wake up. And then you can't get out of bed in the study, so you just lie awake. And then at some point, I don't know if it's through boredom or you drift back off into sleep. And that was argued as a clear demonstration of this split sleep. But as I said, there are awake usually for about six and a half, seven hours. Also, there was no magical awakening period. It's a probability distribution.

And what that means is, if you look at the data, it's just more likely that people will wake up after about six or seven hours. And then more likely that they will go back down into sleep. It wasn't as though the whole experiment demonstrated a very clear termination of sleep that everyone had at that moment in time. So that's the first issue. And the second issue, which is first issue, it's kind of an abnormal thing 14 hours forced in bed. The second is, it wasn't a clear

separation. It's just simply high probability. The final issue is that it was a study done in only seven individuals' healthy males. And so I have yet to see it scaled up. Did it happen? First sleep, second sleep, yes, it did. Is there any strong evidence that's that's how we naturally were designed and have evolved to sleep? In truth, I don't think so. At least I don't see good evidence right now supporting that, but remain open to it.

In episode one, we talked a little bit about body position during sleep. And how different degrees of incline or decline might impact some of the features of sleep. And I can't help but ask now as you described this bifasic pattern for people that were essentially experimentally restricted to the bed. Is there something about being horizontal that makes us sleepy? That is. And it's perhaps not for the reasons that you would think, which is, okay, I'm just

pre-programmed when I lie down in my head, it's the pillow. It turns out that it seems to be temperature that when your body is recumbent, lying flat, horizontal, the distribution of how your body is able to move blood around the different regions and decrease your core body temperature, meaning it can push blood, warm blood out of the core of your body to these surface areas. And when you push it out to the surface areas, you release that heat. It's this huge thermal

dissipation that happens when we move blood out of the core to the surface. You emit that heat and your core body temperature plummets. When your body temperature, your core body temperature decreases. You have a higher likelihood of sleepiness. In fact, it's very difficult for you to fall asleep if your core body temperature does not drop. And by lying down the bodies, what we call vasoactive ability to distribute that blood in a way that is permissive for thermal

dissipation of core body temperature is superior. And that's the reason why we find it easier to fall asleep lying down than, let's say, semi-recombent or certainly propped all the way up. And it's probably the reason naturally we evolve just to lie down on the floor. Very interesting. Maybe Dow's a good time to talk about bifasic sleep in the context of about of sleep at night and the afternoon nap. You've mentioned this post-parandial dip that most people experience between

one and four pm that many people try and combat with caffeine. We'll also talk about caffeine this episode. Such an interesting substance. And I think the most commonly used drug, is it is the drug after all, worldwide. I think more than 90% of adults worldwide consume caffeine on a daily basis. That's correct. And I believe it is after oil, it may be perhaps the second or at least the third most traded commodity on this planet. And it is what we call a psychoactive

stimulant. It is a stimulant. And it's probably one of the only stimulants that we will readily give to our children and not be too concerned about it. We'll get to caffeine in depth a little bit later in this episode. But I can't help but just mention that someone, I think it was Michael Paul and said that caffeine is one of the few drugs that almost everybody takes just to, quote unquote, feel normal. Yeah. Exactly. I think sometimes sleep deprivation is

simply just the absence of caffeine. And so it's a very interesting chemical which I have in truth changed my mind on. And I'm happy to speak about why I've changed my mind. But also some godrails too. And we'll go there. Meanwhile, I'll take a sip of my triple espresso here as we discuss. So we discuss naps. Our naps good for us. Should we nap? What if we don't like naps? Why do we wake up from naps? Groggy sometimes and other times we feel refreshed.

Tell us about napping. Naps are both good and bad depending on the situation. Naps can be a double-edged sword in other words. We and others have done lots of studies on naps and the benefits are fascinating. And standing out, tell you about one study we did, we had participants assigned to one of two groups. And at midday, they all learned a whole list of new facts. So there's a study about learning and memory. And then one group took a 90-minute sleep opportunity, sort of focused

right around that drop in alertness. The other just remained awake, lying on a bed, and they just watched a nature documentary. And then five hours later, we had them do another learning session. And so they've woken up after the 90-minute nap. They've got through that sort of initial lull that we'll discuss what that is after you wake up. Everyone's now back to operating temperature. So in other words, I've had you try to cram in a whole list of facts at midday and then a whole

list of facts, new facts again at 5pm. And I can ask, what is the learning capacity of your brain at midday and at 5pm? And is there any difference in your learning ability when you have had a nap in between versus not? And sure enough, what happened in the group that did not nap, their learning capacity gradually declined across the day. The nap group, they were able to sustain their learning and in fact, if anything, improve it. And the difference between those two groups at

5pm was about 20%. So that's certainly non-trivial in terms of if you're to say, you know, here's a new compound that can boost your learning capacity by 20%. Would you take it? I suspect it would probably make some money. So that's a demonstration of full learning in memory. We did another study very much like that in terms of its design, but we looked at your emotional brain and we were

showing people different types of emotional expressions and having them rate them. And we did that firstly before a nap and then after a nap versus that same time in sort of midday versus 5pm. And another group did not nap. And sure enough, the group that did not nap by about 5pm, they were starting to rate fearful faces and angry faces as much more fearful and much more

angry. But if you looked at the group that napped, it was different. They actually lessened the response to fear and they blunted the normal increase in anger sensitivity across the day. And the nap seemed to boost how positively you rated happy faces. So a nap there had the ability to reset the magnetic north of your emotional compass. And there was a beneficial almost added rose tint to your world view glasses after you'd napped. What was also interesting in those two

studies, two different types of sleep were transacting those benefits. In the nap group that was doing the learning, the learning benefit that they got wasn't just about them napping and sleeping. It was about them having these sleep spindles. The more of those sleep spindles that you had, the greater the restoration of your learning capacity when you wake up. For the emotional recalibration that I described in the nap, that had nothing to do with sleep

spindles or even non-rem sleep. It required REM sleep to produce that benefit. So there are certainly many benefits and we've looked downstairs in the body, blood pressure, cardiovascular measures, immune health. They all seem to benefit. So at that point, everyone may be thinking, of course, this sounds good. Not to mention the basics, which is your attention, your concentration, your focus and your energy will improve by way of naps. Even your decision-making,

you said decision-making. Yeah, even your decision-making is improved. So your capacity to make the correct decision outcomes based on this weight of evidence that you're facing, that's also improved. So almost all areas of cognition that we've looked at and many areas of your emotional and mood health, we've looked at seem to benefit by way of a nap. At that point, you're thinking, so then what's the problem? The problem is that when you nap, you release some of that sleep

pressure that's been building up. So in the first episode, we spoke about a chemical called adenosine and the longer that you're awake, the more adenosine that builds up, the more adenosine that builds up, the sleepier you will feel. After about 16 hours of being awake, you should have lots of healthy sleepiness of adenosine in your brain to put you asleep and keep you asleep. And when we sleep, we are able to clear that adenosine from the brain. So we wake up after

seven to nine hours. And if it's being good quality sleep, we're refreshed because we've cleansed the brain in part of that adenosine. When you take a nap, like a pressure valve on a steam cookup, you just release some of that healthy sleepiness that you've been building up. So the dark side of napping is if you are struggling with sleep and you suffer from insomnia, the advice is do not nap during the day because you're setting yourself up for an even higher

probability of failure at night. Why? Because when you nap, you release some of that good sleepiness that we need to build up for you as someone who is struggling with sleep to give you the greatest chance of a weight of sleepiness on your shoulders. So if you are not struggling with sleep and you can nap regularly, I would say naps are just fine. And we can unpack what is an optimal nap and the protocol for what napping should be. I would say that's great. The only caveat is make

sure that you're not napping too late into the day. And this is one of the components of the protocol of how to nap because napping late in the day is too close to sleep. And you can think of it almost like snacking before your main meal. And nap late in the day just takes the appetite edge off your sleepiness so that when it comes time for sleep, you're not as hungry anymore.

So just keep that in mind. But we can unpack perhaps the optimal way to nap if you are going to nap and exactly the dos and the don'ts of that if that sounds of somewhat interesting. Yeah, that is of immense interest to me and I know many other people. I'm a huge believer in naps. I've always enjoyed short naps of about 10 to 30 minutes unless I'm somehow sleep deprived in

which case I will sleep for an hour or even a little bit more. But I make sure I set an alarm really based on advice that you gave me which was to first of all decide whether or not a nap is beneficial for me or for whoever is considering that. But then to make sure that however long that nap is zero to 90 minutes that it not be longer than 90 minutes because the real goal is to not disrupt nighttime sleep. That's right. Which is essentially just a more long winded way of saying

what you just said. So how does one determine the optimal duration of nap? And in particular to avoid the problem of disrupting nighttime sleep by napping. But also this rather common phenomenon of waking up and feeling kind of groggy or even kind of grumpy. I get the post-napped face or we should call the post-napped expression. Pne. What's your Pne? Do you wake up in the morning too? Some people wake up and they're like that face and then there's the like

good morning. And I think people that wake up with the good morning are particularly delightful unless you're of the post-napped expression that is kind of the crumpled face and then you just don't want to be around those. Yeah. This probably relates to spirit animals and things like that. Some people wake up like a cheerful chipmunk and other people seem to wake up like my bulldog Costello words. Jowls still in contact with the floor. Yeah. So Pne. I'm trying to hold it together.

I'm not absolutely just full of thought. It's brilliant. Please trade market. So firstly to your question, how to optimally nap. The word optimal is interesting because when you people say how long should I nap? What's the optimal nap duration? The question I have back to them is what are you trying to optimize? Because once I understand what you're trying to optimize, I can give you a better prescription, non-medical. I'm talking about here, the better sort of

you know, protocol piece of advice for how to nap. I mentioned the study about emotional faces in part for a specific reason because I told you there the benefit came by way not of non-rem sleep but REM sleep. And in our first episode we said that when you go through these on average 90 minute cycles, you get most of your non-rem sleep first and then you'll have this bout of REM sleep at the end and it always seems to go that way when you are healthy normal person. You go into

non-rem sleep and then you go into REM sleep. It's very rare that you ever go directly into REM sleep. There are only two reasons when that seems to happen. The first is a clinical condition called knuckle upcy where you can have sleep on set, REM sleep and it's very rare. The second is if you are horrifically deprived of REM sleep night after night after night, I let you sleep then. At that point, REM sleep, the pressure for REM sleep has been built to the point of being almost

just insatiable and your brain goes straight into REM sleep. But with those two things aside, you go into non-rem sleep first. So I brought up the emotional study of resetting your sort of mood compass because to get that REM sleep you had to nap for a longer period of time because you had to get through the non-rem sleep first before you get the REM sleep. But let's come back to then assuming optimal is for most people when they speak about naps, I just want the quick reboot.

I want my alertness and concentration which are failing because I'm staring at the screen or I just can't concentrate on the work that I'm doing. I want my alertness and my concentration to be improved. I want that sort of slight boost in brain energy where I know I can sustain myself for now a longer period of time and I've got the motivation which is relieved in some ways how I like to think about energy as well. I've got the motivation and the drive to keep going which is just

starting to fail me. To get those basic things which is what most people nap for aim for a 20-minute nap. Why 20 minutes? If I thin slice the nap duration and those studies have been done where we look at essentially what's called a dose response curve, I give you five minutes of a nap, 10 minutes of an nap, 15 minutes, 20 minutes, 30 minutes, 45 minutes, 90 minutes. After five or 10 minutes,

you don't really get very much. You will wake up and you'll have some degree of improved alertness and your basic reaction time may be a little bit quicker but that fades very quickly and you don't sustain that benefit. Once you get past about 15 to 17 minutes now things start to look different. You get these nice benefits for concentration alertness and motivation and those things

sustain. Once you wake up out of that, probably really I would say 20-minute nap. At that point you've got some good wind in your concentration and energy sales for the brain and that will sustain you throughout the rest of the afternoon and into the evening. The benefit of the 20-minute nap is that you don't get the Pne, trademark Andrew Huberman, you don't get that almost

sleep hangover. Some people will say it's strange, I nap, maybe on that 45 minutes, 50 minutes and I wake up and to be honest Matt, I almost feel worse after the nap that I did before and I don't understand it. It's something called sleep inertia and an extreme version of this is in the first two hours of your night of sleep you get a phone call or an alarm goes off and you wake up and you

are just kind of lost in the ocean. You're looking around at your surroundings, you're just in this groggy state, you're half awake half asleep and you can respond and you can do things but boy, does it feel miserable and it's almost as though you're going from the ground floor right up to the penthouse suite but you get stuck somewhere in between kind of floor 13 and it's this rough state.

If you go out into sleep, light stage one non-rhyme, then stage two non-rhyme and just before you get into the very deeper stages of non-rhyme three and four that starts to happen around 30 to 40 minutes

for most people. But by cutting your nap off at 20 minutes, you still get these nice benefits from a good chunk of healthy non-rhyme sleep but you're not going so far into the cycle so deep into your non-rhyme that when you wake up after 20 minutes, you're not in that what we call sleep inertia phase,

that sleep groggyness, that sleep hangover phase. So it's a nice benefit that you get all of these improvements in your brain but you wake up and very quickly you're back up to operating temperature and you don't suffer that inertia. Now that's not to say that when you sleep or you nap longer, you don't start to get more benefits you do and those benefits are both greater in their magnitude

and sustain for a longer period of time they do. It's just that you have to understand the trade-off that you will suffer which is I will get more bang for my book and I will get more benefits but I will in the first sort of hour or so have to understand that at that point I may even be functioning worse than that which I did before I even started napping but if you're patient and

you go through it the rewards on the other side are significantly better still. So that's the first piece of advice and when it comes to how to nap I would say the dose and the timing make the poison and poison is hypergly and here it's simply just the poison being how much sleep inertia going to suffer. So aim for about 20 minutes that's the dose the timing comes back to that which we describe

before do not nap too late into the day. So what's the rule of thumb here for a protocol? On average for the average adult I would say don't nap after about 3 pm. 20 minute naps, sometime between 3 pm and if you're struggling with sleep don't do this at all if you're not and you're able to get

to sleep fine this seems to be a good ingredient for the basic return on your investment. Again if you tell me what's the optimal nap duration we need to have a conversation to understand what is it that you're going after here what are the benefits and then I can sort of you know create a finger buffet kaleidoscope match to what you need and we can think about the nap duration as a

consequence. Thank you that's very informative I have a colleague at Stanford who's a Howard Hughes investigator which for those that don't know is a rather elite club of academic researcher they have to essentially try out for it they can every five years they go up for renewal it's a lot

of money which makes them gives them a greater capacity to take on greater risk work higher risk work and he's also a member of the national academy and he was one of these people graduated high school at 15 years of age one of these phenoms and he is so religious about his napping such that when he

travels to give seminars at other schools he insists that they schedule a nap time for him after lunch and in his office you know between 1230 and 1pm he's napping everyone knows this and I mentioned this because I think that oftentimes people think of the nappers as the lazy ones but

his output is near superhuman and he attributes much of that output to the nap not just the post nap work that he's able to perform but his ability to just kind of manage so many ideas he has an enormous laboratory and that's just one example I think they're examples from sport of sprinters

taking naps on the you know on the side of the track field I mean so it seems that a capacity to nap is also something worth considering because I think many people listening to this are thinking well I can't nap should I nap you know and can one teach themselves to nap so that's

the question if one would want to explore napping and is that something that one should even consider doing if you don't have a propensity to nap should you avoid it if you want to try naps how could one teach oneself to nap you just mentioned earlier lying down relates to body

temperature body temperature relates to sleepiness and then as a third question I promise I'll repeat these if we need to as a third question I'd like to have a little bit of a discussion about some of the pseudo nap states that I certainly am intrigued by you know for instance just lying down and

I'm doing a progressive bodily relaxation things like yoga nidra non-sleep deep rest which is an acronym I coined simply to to make it clear what I was talking about but it's very similar to yoga nidra things of that sort in other words but simply should everyone think about having an

early to mid afternoon protocol to reset their cognition and their body we call it a nap but does it have to be a nap and if we're not good nappers should we try and if so how should we go about it yes so two or three questions firstly if you're not a natural napper should you

start doing it if you want to start doing it how should you do it and then the third is is the some kind of you know substitute for a like kind which would be these I'd love the phraseology that you use these liminal states do they mimic that are they different to that how should we think about

those the first thing I would say to point number one if you are not a natural napper don't necessarily force yourself to be as long as you're getting the sleep that you feel you need at night and you feel refreshed and restored during the day and you don't have that sort of post-prandial drop to the point of thinking I almost need to nap during the day there is no pressure based on anything I've been telling you for you to start napping nor should there be any reason that you do start napping

but let's say that you want to try what would be the right protocol to improve and increase the likelihood the best way you can do this is to mimic night time as best you can so wherever you are if you can shut off the lights make sure that you can block out you know curtains

blinds if you can't do that fully and many people won't be able to develop an i-mask procedure so put an i-mask on make sure you block out noise earplugs you can use a sound machine if you want and we can speak about sort of sound machines and whether or not they're good or

bad on sleep and then you can lie down make sure that you try to take your shoes off and get under some kind of a blanket because we're so contextually queued by having something wrapped around us called a blanket or a duvet that to do it without that if you are not a natural napper

can help you again that some people say I can just kick my feet up on my desk sit back in my reclining chair in the office and I can fall asleep that's great but if you're not a natural person I'm just trying to tell you things that increase the probability of that and then set the alarm

I like your idea of making sure that if you do fall asleep you don't accidentally go too long and then just feel miserable so mimic the conditions that you're trying to get that you would normally get at night that will increase the probability mask out noise mask out light kick your

shoes off have some kind of a blanket wrapping around you that's probably the best and then time it based on this sort of post-prandial drop you will know yourself everyone has fallen prey to it you know well it's usually around about three four pm that I do start to feel this decline or it's

around one pm try to match it in accordance with that so there's the first I think two questions should you not necessarily if you would like to and are not normally doing it how can you do it the final point I think is fascinating which is these alternate states of

conscious brain activity the most obvious is when we're awake and when we're asleep those are the two most dramatic changes in consciousness that we experience on a daily basis short of anesthesia I've become like you very fascinated by these sort of both meditative states or these

liminal states I think at some point you and I should collaborate and we should do some work and really unpack this but the reason I find this interesting is because I'm going to guess you are having sleep like states but you are not fully asleep how would I define a sleep like state what

we've learned is that your brain the way it sleeps isn't on mass it's not as though your entire brain sleeps different territories of your brain can sleep in different ways and what we've also known and the some argument even individual brain cells seem to have a period

where they go into sleep and these individual neurons will start to show what look like these beautiful big powerful deep slow waves in terms of their firing rate at least in terms of those neurons firing away I bring this up because if that means that your brain can have

local sleep rather than global sleep if you are in global sleep you're out like a light you are a sleep but perhaps these liminal states the reason that they give these benefits is because you are still awake not global sleep so if you're in global sleep you're asleep but you're awake so you're

not in global sleep but you may be having local sleep now using special setups in my laboratory we can apply tens maybe hundreds of electrodes all over your head and we can map the different places where your brain is having sleep in much higher resolution so rather than a 480 dpi movie

on YouTube I'm now in 4k resolution I can really dismantle what's going on analytically in your brain I'm going to guess that when you're going into these states and you report coming out of those states and I ask you on a scale of 1 to 10 how would you rate that as an experience based on

your common experience the greater the intensity of the liminal benefit and state that you experienced I'm going to predict is directly related to the extent of this this local deep non-rem slow wave sleep that's happening you're still awake but some parts of your brain for maybe seconds

of time or maybe even tens of seconds of time I'm going to bet we'll be oscillating in what look like slow wave sleep deep sleep states and if all I would be able to look at is that one part of your brain and that small cluster of electrodes and someone said to me is this person awake or a sleep

I would say oh they're asleep they're in deep sleep but then if you slowly reveal and back out and show me the rest of the brain and what it's doing I would say oh my goodness no this person must be awake but that local territory that district up there in that brain they were having

slow wave sleep I think that's what we could find and that may predict some of the benefits that you get some of the productivity energy benefits by the way I should note that with all of this nap racket NASA figured this out back in the 1980s they were looking at ways to optimize their

astronauts because when you are up in orbit depending on what orbit you're in you are rotating around the planet maybe 10 20 times per 24 hours so you're seeing 10 to you know 20 sunsets and sunrises so your sleep is a total mess and you can safety check almost everything in terms of

technology but the one weak link in a space mission is this thing called the human being that's where errors typically happen so how do you de-risk a human error up in space because if you make an error up there I mean on the ground not great up there kind of catastrophic you can try to

optimize the ability to sleep and their ability to maintain focus concentration alertness and productivity and what they found was that these naps produced almost a 20% boost in short naps 20% boost in their alertness and almost a 50% boost in their task productivity and it was so

powerful that it translated to the terrestrial employees of NASA on the ground and it became what was known as the NASA nap culture and from there on we had what were called power naps power naps by the way why have they called power naps and you think well just because it powers me up

it's a good idea but it's wrong it has a very specific story of fascinating one two legends in my field David Dindjus and Mark Rose kind they were looking at how to instigate risk mitigation not in astronauts but in pilots who are doing long haul flights because the most dangerous aspect of

a long haul flight is when it is coming down to land and that's when they can sometimes have these things called a catastrophic whole loss which is a euphemistic phrase for a terrible plane crash and they were trying to say how could you use naps strategically to de-risk that and improve

their alertness and they asked a very interesting question if they can nap for only a certain period of time because they have to be at work on the plane for the rest of it when should you place that nap should you do it at the start of the long haul flight in the middle or towards the end

and most people would bet like they I think did it's best to place it at the end when you're really starting to struggle get that boost and then you wake up you're not in sleep inertia because it's been brief and then you are energized for landing they didn't find that they found that the most

optimal time to nap was early on in that long haul flight and it sustained them throughout the rest of the flight now they took their findings to the FAA who are funding the work and the federal aviation authority here in the United States and they said we've got some great findings and we

think we should implement this and we would like to use a term to help pilots understand this and it's called prophylactic napping and of course there were many chuckles throughout the room perhaps inappropriate and they just said look you can't understand our pilots that you know kind

of alpha male guys and if you're starting to say you need to prophylactically nap it's not going to be adopted that's a no go so they looked around the room because it's an alpha male culture it's a mostly masculine culture at that time they said what could we and there's a lot of beard stroking

and they said I've got it power naps it's got to be about power and so that is where if you've ever wondered where the term power naps come from it's not because it reboosts your power which it does and boosts it back up it's because there was chuckles at the time prophylactic napping I'd like

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of things fascinates me especially in the landscape of health and well-being also and that's one reason why having become a real fan and practitioner of yoga nidra which I think translates to yoga sleep which is this process of lying down for a period of 30 to 60 minutes progressive relaxation

this is these are scripts that are readily available as this is a age old practice in in India that is meant to restore mental and physical vigor vigor I place you one into one of these liminal states the and I've great respect for the nidra to tradition but sometimes the names

are a separator so people who hear yoga nidra and they think it must be yoga movement and that's of course not true where they think that there must be some mystical component to it which is not necessarily true sometimes they include intentions and things like that but often not so that's

why I coined this phrase a non sleep deep rest which is essentially maintains the critical components of yoga nidra but doesn't include intentions and has a shorter 10 or 20 minute protocols so it'd be great fun and I think very interesting for us to do that project to explore what are the brain's

activation states or deactivation states as the case may be in these non traditional or liminal state practices now along the lines of power napping specifically in the naming of power napping I think it's more than than just an anecdote because I think it is very important for

people to understand that these protocols these tools that NASA and that laboratories have have developed oftentimes are for other purposes but they translate to a kind of broader significance and what I'm hearing and what I'm starting to integrate as we have today's conversation is that

it seems that there is pretty good reason to at least explore bifasic sleep right that for the non nappers to really think about whether or not they would like to explore napping as you mentioned they don't have to and then for people who are already napping to really think about the

placement of that nap within the day and the duration of that nap what you told us a few moments ago suggests that I should be doing or anyone that's doing naps or entering these liminal states like nsdr might want to shift them a little bit earlier than the period in which they first become sleepy to take that nap is that right I mean like so for instance should I do as my colleague and you know finish lunch and and lie down for 10 15 minutes rather than wait until 2 or 3 p.m.

Is that is that something that could make a meaningful difference? I think it could and I think it really again depends on how much of a struggle sleep becomes in the evening for you if it is becoming the later that you nap if your sleep becomes either a more difficult to initiate in the evening or maybe you don't have any problems falling asleep

but for some reason when I look back I'm now starting to wake up more throughout the night that in part again it's not just that if you nap late in the day you struggle to fall asleep you may nod the other consequence that can happen which is non mutually exclusive is that you then stay

in not as deep asleep and your sleep is more fragile in that sense so the probability that you will wake up because you have the nap so late in the day is higher in the middle of the night and then when you wake up like many of us do and you go to the restroom or there's perfectly natural

but the speed with which you can then fall back asleep is compromised why because you jettison some of that sleepiness by way of the nap and there isn't as much to take you back down into sleep after you've woken up so I would just say that if you are seeing that pattern that the later

napping that you're doing if you're doing that and again there's no reason that you need to nap only if you choose to nap if that's the case then consider not necessarily obviating the nap that may not be required just bring it back earlier take it after lunch see how things work out do the

experiment and when you do the experiment make sure that you do what I would describe as the on off on experiment which is where you're napping as you normally do and you've noticed perhaps some problems with your sleep then do so that's sort of the the the what's sort of the on off on phase

so then change your nap protocol and move it earlier so now you've switched off your standard protocol and you've moved on to something different so you're on your standard protocol and then you come off it and when you come off it meaning you go to an earlier nap and you say gosh things

do seem to be better maybe he had something there and it does seem to improve good but I don't trust that because maybe it's just a placebo effect that you you know here's some dulcet British tones and you get convinced that maybe that would work and you've now instead after about two

weeks of doing that and things have improved go back to your original schedule go back on to your original protocol I'm not as interested about the fact that things got better when we changed it I'm interested in the question do things get worse when we stop it and so when we stop the intervention

if things got worse again now I'm I'm believing it a lot more so just as a tip if you are a self-tinker and so you don't have to do that but if you're idiotic and like me and a scientist and you want to do it with this city rigor that's the way I would suggest doing it I don't think it's idiotic at

all I think it's systematic and what you just described is both a negative control and a positive control experiment so you're you're a scientist to add the terms through and through are there any individuals that should absolutely avoid napping you know I've a perred lore of you know elderly

folks folks with certain conditions you know I can't imagine which but I'm sure you'll tell us that for whom napping is harmful to their health it's a very I think interesting question because the strongest evidence comes back to that which we've mentioned before which is insomnia and really

the recommendation there is just avoid naps it's and what's problematic about insomnia when you are having such tough times with sleep at night and you are just dragging through the day it is miserable and I am you know I I'm very protective of my sleep for the most part I sleep pretty well but I've

I'm I'm I'm not immune to the vagaries of sleep I've had two bouts of insomnia throughout my life both of me and what we call reactive insomnia reactive to an event or something happening and I know how just desperate and hungry you are for sleep and if it's happening

week after week month after month I'll just do anything to get sleep when I can and the temptation therefore to nap when you are suffering from insomnia is that much higher and therefore the advice is that much harder to adopt but trust me that is one of the components that we have in the

psychological treatment bucket that we use for insomnia which is called cognitive behavioral therapy for insomnia or CBTI for short and you can just look it up or on my own podcasted in a six part series on on insomnia so I would say try to back away in that circumstance but

you brought up another example which is in aging there I think the evidence is a little less causal so you have to be more cautious about recommending the absence as I was with insomnia of abstaining from naps but the data has now become quite strong that when you get past about

65 years old and you look at napping behavior in large epidemiological studies and you say is there a positive benefit in aging for napping or is there no benefit at all and they looked at that because they thought well that perhaps based on the work in healthy adults that I've described

that would be good for older adults not only did they find that it wasn't good they found that it was deleterious that napping in older adults was predictive of worse health outcomes and it also seemed to predict a higher likelihood of early mortality so at this point we're thinking

well how does that fit with everything you've been telling us it comes back to this notion of bad sleep at night it's probably not necessarily that napping during the day is bad for older adults it's that the naps reflect a problem with the night of sleep for older adults and as we get older

something I didn't mention during development was that yes we get this sort of stable ratio of four to one of one part REM sleep four parts non-REM in our seven to nine hours and I describe these changes in REM early in development I didn't mention two things about non-REM slow wave

activity first as we go into our teenage years and we shift our sort of timing of sleep where we want to go to bed later and wake up later that's biologically determined it's not teenagers fault something happens with their deep sleep however their deep sleep starts to do a different

or different action to the brain that REM sleep was doing as an infant I said that during infancy we have huge amounts of REM sleep and we're growing synapses synapse genesis and we're wiring up all of those new territories all of these new neighborhoods with fiber optic cable but let's say that

you've now run the experiment across many years through until teenage hood of those neighborhoods and you've been measuring the bandwidth consumption of each individual house and you've started to realize well I wanted to create a big spread across the brain and then I'm just going to let

experience over the next years time tell me which parts of the brain seem to enjoy that high bandwidth and which parts don't seem to use it very much and as we go through into our teenage years we go through something called synaptic pruning where the brain actually calls and takes away

synapses from certain parts of the brain it seems to be that this change in slow-wave sleep that happens around these adolescent years is performing the act of final cortical maturation that it's downscaling the synapses and fine-tuning the brain so you've got this beautiful efficiency and now

you've throttle back some of the bandwidth from some of those neighborhoods because they just don't use it very much and you can move it over into the territories that are demanding more bandwidth and net net the brain is downscaled but it's improved its efficiency in the sense that those

regions that needed on our working hard based on what we think this organism has been doing over the past 13 years that's where we need to now place our bets but as we get through into our old years and this will come back to this issue of napping don't worry stick with me here folks the reason

is that as we're getting older our sleep declines but it's not just all sleep declines deep sleep declines most dramatically and we all think of aging from brain perspective as cognitive decline that are learning and memory abilities begin to fade and decline and they do but I would argue that

a physiological signature of aging is that your sleep gets worse and particularly your deep sleep what's perhaps concerning for people listening to this right now is that that decline in deep sleep doesn't start happening in your 60s or your 50s or even your 40s we can start to pick up that

great sleep decline beginning in your mid to late 30s and then it just decreases and by age 50 you are down to about 50% of the deep non-rem sleep that you were having when you were 17 or 18 by age 65 and over or certainly by age 75 you are down to about just 5% of the deep sleep that you had

when you were 17 or 18 just a stunning decline what that means comes back to the first episode we spoke about the four macros of good sleep quantity quality timing and regularity one of the measures of quality that I described to you was this electrical quality of deep sleep the other measure

of quality sleep I spoke about was how consolidated and consistent your sleep is versus how fragmented your sleep is the measure of sleep quality is markedly compromised as we get older we're waking up many more times our sleep is much more fragmented and therefore our sleep efficiency is worse

and we've got this huge decline in our deep non-rem sleep so no wonder then when you are awake during the day as an older adult your sleep quality is so compromised at that stage you perhaps try to compensate by way of napping but that compromised quality of sleep that you're having at night is

probably the reason that you start to get sick more that you have a higher probability of illness and disease and why also you probably have a higher risk of premature mortality so in other words it's the bad quality of sleep at night that leads to this behavior that we call daytime napping

in older adults that seems to indirectly suggest oh my goodness it's daytime napping that's bad and that causes these problems when in fact it's that daytime napping is a proxy for the bad sleep that's happening at night and it's really the bad sleep that's happening at night that is more

directly related to the health and mortality concerns in older adults so that's why I think right now as a field I'm still open to evidence that napping for some reason that we just do not understand right now is problematic and does causally predict worse health and a shorter life

span in older adults I think the best evidence that we have right now is that it's actually the bad quality of sleep at night and thus we should not be necessarily jumping to recommendations that all older adults should stop napping I think we need more evidence and I've opened to both sides of

that let's talk about caffeine I've heard the term is it napucino yeah I think it refers to a practice of drinking some caffeine then laying down for a nap and then supposedly waking up feeling more refreshed my understanding and you'll tell us more of course is that caffeine

is effectively an adenosine antagonist although it's a competitive magnetist you'll explain yeah I'm sure and napping as you mentioned before remove some of the sleep pressure aka uh wipes away some of that adenosine that's accumulated both of which sound great but as you

mentioned earlier there's a warning there as well the warning label on both those things should be that having sufficient adenosine built up in your brain is one of the ways in which you feel sleepy at night and fall asleep and stay asleep yeah so what's the story with caffeine how does it

work to make us feel more alert and what is the rationale for the napucino the napucino also known as the caffeine nap caffeine is a very interesting compound in relationship to sleep and wake obviously everyone knows that caffeine can help you stay awake it's no coincidence that those two

words that you've used about these chemical compounds caffeine and adenosine sound the same it's because the receptor that or the receptor systems that caffeine targets in your brain are the adenosine receptors and you think well Matt was telling me that the more adenosine that builds up

in other words the more adenosine that's latching on to those adenosine receptors in your brain the sleepier that you feel and i'm telling you that caffeine works on those same receptors that doesn't make sense caffeine if it's working on those same receptors should increase your sleepiness

it doesn't because it when it binds on to those adenosine receptors those welcome sites in the brain it simply blocks them it doesn't deactivate them nor does it activate them it simply blocks them so think about it almost a little bit like a room that's full of chars and at some point these

adenosine which is one collection of people with the name badges of denocene they would normally like to come in and start sitting down on those seats which are the adenosine receptors and as they sit down on those seats you're building up this signal of sleepiness well caffeine which is

another group of people with caffeine badges they race into the room and they start to hijack the seats and they start to sit down on them and all of a sudden adenosine can't find any seats to sit on so your brain is still flooding that room with adenosine so the adenosine is still building up

but the reason that you don't feel sleepy anymore when you've had a shot of caffeine is because caffeine is raced in it's latched on to the receptors and it is essentially hit the mute button on your sleepiness so now your brain was thinking gosh I've been awake for about 13 or 14 hours

I'm starting to feel it I'm just going to take a quick espresso shot and you get that you don't think well hang on a second you know 20 30 minutes later I don't feel as tight anymore why it's not because caffeine came in and removed the adenosine it didn't caffeine has come in blocked the

sites but the the adenosine is still building up and then at some point the caffeine was off and therefore not only do you go back to the same level adenosine of adenosine that you did two hours ago it's that plus the additional two hours of adenosine that has been building up

and what your experience is something called a caffeine crash and now you need even more caffeine not just to get you back to where you were but to recover the crash that you've had and go further caffeine in relationship to the caffeine nap though the napachino is relevant because of its timing

caffeine caffeine has an instigating action of around 12 14 to 17 minutes so when you come through in the morning and you grab your first cup of coffee and within the first four or five minutes you say I just I just feel better I've just had a couple of sips I've had half a cup

of coffee and I already feel better I just needed that if it's within the first five minutes that you're experiencing that it's got nothing to do with the caffeine because the peak plasma concentration if your caffeine is not going to arrive with you until about you know 12 to 17

minutes so why do you feel better some of it is placebo because you're smelling the coffee and you associate it with the lense it's really not that though or or when you say placebo I also wonder whether or not it's possibly a conditioned effect you know it like a Pavlovian thing because

the smell of the coffee the taste of the coffee the the the honey of the machine are they're walking into the cafe to and ordering it from the barista also creates an anticipatory arousal like the the the alertness is coming and in that anticipation there's its own form of alertness I think that's

that's certainly a big component of it the other component however if you look at the data is that it's got nothing to do with the caffeine in that moment it's the temperature that most people take that caffeine warm either it's tea or it's coffee or it's perhaps something else that Andrew

Hugo would drink but many people your bama tays since I since I was five years old I don't I don't know if I should have been drinking a caffeinated your bama tays so young maybe even four years old there's a photo of me on my grandfather's lap drinking out of the manteigord half my family's

Argentine and so I was caffeinated from a young age this brain developed in a caffeinated mili this explains so much about what I've known of you over these you know I'm kidding you so but we need to speak later no so what's interesting about that is it's the temperature

and I told you in the first episode that we need to cool down to stay asleep but we need to initially warm up to fall asleep because warming up at that moment I was telling you is warming up at the periphery warm up to cool down to fall asleep so you need to warm up to cool down to fall asleep

then you need to stay cool to stay asleep and then you need to warm up to wake up the warming up to cool down to fall asleep is not warming up in the middle deeps core of your body it's about warming up the hands and the feet and the head to dissipate the heat hence warm up the outer surfaces

to cool down the inner core to fall asleep but then I told you you have to warm up to wake up and when we take a hot drink in the morning usually caffeinated the change in your core body temperature can happen within a handful of minutes so the initial benefit that you get from the

hot cup of coffee in the morning or hot tea is from the temperature rise and then you get this beautiful second kick from the caffeine itself and that caffeine can then sustain for a longer period of time so we mentioned this problem with napping that even at sort of 25 or 30 minutes of a

nap you wake up with that kind of groginess that sleep inertia and what however if I could give you the benefits of a nap and have you come out of the nap with zero sleep inertia and that's what some folks started to clearly think about what if I could look at the timing of the optimal nap

maybe 20 minutes and think about the timing of when peak plasma concentration of caffeine emerges and I told you it really starts to kick in to gear around 17 minutes and it's in full swing by 20 what if I was creative I'm going to withhold from saying idiotic enough but creative enough

to get into bed just before I turn the light out for my nap in the afternoon I swig a quick espresso light goes off I close my eyes I mask ear plugs and I'm going to drift off fine because the caffeine is not going to kick in for another 17 20 minutes perhaps it's full threshold

so now you you fall into sleep and you're going down into sleep and if you perhaps don't make it too large in terms of it serving the temperature change is not going to affect you in a negative way and then just as your alarm clock is about to go off after 20 minutes you're on the beautiful

ascending swing of upward plasma concentration of caffeine and you get ejected out the other side with both the benefits of the nap together with the benefits of the caffeine so you get your cake and you can eat it too you get the nap absent the sleep inertia and hence this created what we

call the caffeine nap love it the napachino the napachino um maybe I'll give it a try this is the first time I've ever heard the the rationale and the the fine structure of the napachino but it makes sense at a logical and mechanistic level I have to ask is there anything besides caffeine

and sleep that can clear a dentisine you know can exercise clear a dentisine can cold shower clear a dentisine I mean I understand that there are a bunch of competing mechanisms in the body like presumably a spike in norepinephrine or adrenaline or both is going to impact the

dentisine system I once heard a great quote from a former uh member of the national academy of sciences a brilliant guy he said you know a a drug is a substance that when injected into an animal or a human produces a scientific publication meaning meaning it is it is rare to

find a paper that doesn't see some effect of some drug especially on sleep I'm told as I recall if you put aspirin REM sleep into PubMed you're going to see some effect on REM sleep people take aspirin pretty much any substance that one takes is going to alter some feature of sleep or of wakeful states if one is looking with a fine enough instrument or is that an overstatement?

No I don't think it is no for statements and it comes back to the first episode where we describe the complexity this incredible beautiful physiological ballet certainly one of the recommendations when people say I get this afternoon this post-prandial drop in my alertness what can I do I can see you could nap but another way is just get outside and walk around be physically active some of that has to do with the fact that you'll probably get some daylight and daylight can be a stimulator of

alertness as long you've told us and educated us on we also know that physical activity by itself can increase the amount of endorphins and dinoffins and those are wake promoting but none of those are really necessarily going to be altering a denocene they're simply overriding the adenosine

that is still building up it really does seem to be for the most part at least as all that I know it's only sleep and particularly non-rem sleep that has the capacity to or give the brain the chance to remove that adenosine now what could be interesting I think is two circumstances

one is where your brain becomes less metabolically active for another reason and I told you that it's not during it's not as though during deep non-rem sleep that there is some special pulsing cleansing mechanism for adenosine there is a cleansing system called the glimphatic system which

removes the toxic metabolic byproducts of the waking day wakefulness in some ways is biochemically low-level brain damage and sleep is sanitary salvation in that regard but which is again it's heuberistic and it's going too far but it makes a point the idea here however is that it's not

that there is a special system that is removing the adenosine during deep non-rem sleep it's just that your brain is less metabolically active and therefore it's not producing as much adenosine so the natural mechanisms that are always occurring in the background to be clearing adenosine

and degrading it simply get the chance to do that just as effectively as they have but you're no longer working against the opposite tide that is growing the adenosine now the adenosine increase has dissipated because you're no longer metabolically active during deep sleep and you get the chance to cleanse it all of which is to say therefore that and I think that would mimic that such as for example anesthesia my guess is that you probably do jettison some sleep pressure when

you are in anesthesia I also think that these liminal states non-sleep deep rest could be a fascinating territory there because at that point I'm going to guess and we'll be able to see with the EEG and we may also be able to do some imaging depending on how we you and I design the study

to look at what changes in the brain in terms of its activation state my guess is that if it does put you into something like slow wave activity patterns that means that those territories of the brain are metabolically less active and that allows the brain to dissipate the adenosine

so to your point I don't think things like necessarily exercise or light change adenosine levels they do give a nice alertness benefit for the reasons but is there an alternative way of dissipating adenosine yes I think anything that mimics a non or a less metabolically active

brain could produce these beautiful adenosine benefits thank you for that this brings me to a question about the period immediately after waking from the nightly bout of sleep I've been touting the benefits of delaying one's caffeine intake by 90 to 120 minutes after waking there's

a little bit of a misconception out there I think people ran with the ball assuming that I was mandating this or I think or suggesting that everyone should do this and that's simply not the case I actually wake up and I'll hydrate and drink caffeine very close to waking if I'm going to

exercise soon after yeah which I often do but I've experienced and I know others have experienced if they are not going to exercise immediately or they don't need caffeine to exercise for whatever reason I've heard these people exist I'm no such mutant that delaying their caffeine intake by 90

to 120 minutes in some cases can offset the afternoon crash now I want to be clear some of that may be offsetting the afternoon consumption of more caffeine because by delaying your caffeine intake in the morning then perhaps there's less of an incentive or requirement to drink caffeine

the afternoon and all of which dominoes to as we'll talk about more in this series to better sleep at night because you you're not ingesting caffeine close to bedtime but at a risk of taking a massive tangent here's what I'd like to know based on what you just told us if indeed

sleep and lower metabolic activity in certain brain regions can help reduce adenosine levels in the brain one could imagine that upon waking it is either a step function from okay you know let's say it um the 545 am somebody is asleep and adenosine is still being

cleared away because they're asleep and then they wake up boom does adenosine clearance immediately stop well for people who have that crumpled face uh groginess um and they wake up at 545 maybe even by way of alarm although we don't uh suggest that right and they're stagger into the kitchen

and um or nearly they'd make their cup of coffee but they're in a pseudo sleep state so it's dance to reason that they're still clearing adenosine now if they are to drink caffeine right away then they're as you pointed out going to block those adenosine receptors and there's going to be

a continued buildup of adenosine as opposed to a clearance of adenosine right so this was um part not the entire reason but part of the rationale for suggesting that people at least explore delaying caffeine slightly and then there are things like the cortisol rise and etc but um does that

kind of framework at least make logical sense that doesn't mean it would hold up in a randomized controlled trial but given that we're talking about essentially zero risk protocols here um what are your thoughts on that i think it is good advice for people to test and it's good advice for two

reasons the first is that which you describe in some ways by taking caffeine on early and masking that adenosine also caffeine can make your brain more metabolically active which means that you're going to build up more adenosine during the day which means that sleepiness is going to

arrive earlier which means that perhaps that post-prandial drop is going to be you know harsher and you're going to perhaps then need to self-medicate with more caffeine to and so goes the vicious cycle so i think that's one thing to keep in mind i think it's one hypothesis i think

the second hypothesis for me or the second reason i would advocate for that is if you've been using caffeine that way for a long period of time you may also be masking the quality of your sleep because you wake up you immediately medicate with caffeine and you are alert you're awake and you

think well i i'm looking back on my night i'm awake now after my caffeine and now is the important part of that sentence i'm awake now so there's nothing wrong with my sleep is that true maybe it is maybe it's not maybe if you abstain from caffeine through and you have to get through the detox period it's not going to this is not the right test immediately but do it for about two weeks and then at that point once you're free from the detox and the withdrawal now you're in a somewhat naive state

where you're taking your caffeine on i'm not telling you to stop caffeine you're taking it on at 11 o'clock after you've woken up let's say seven o'clock in the morning at that point we've now got this nice clear window that has been consistently happening between seven to 11 in the morning and

i'm going to ask you now do you feel rested restored and refreshed and can you operate with cognitive acumen and skill in those first morning hours now don't forget we've got to get past the natural sleep inertia period in the first 90 minutes but after the first 90 minutes of waking up absent of

caffeine let's say by nine a.m. in the morning are you functioning well because if you're not and you still think you know what i don't feel restored by my sleep i feel unrefreshed i want to then start asking you let's take a look at your sleep and let's see how we can get you to a more

refreshed state and by using caffeine first thing in the morning you don't give yourself the chance to test whether or not subjectively youth sense your sleep is good quality now you don't need to do this forever you can just do a test for a month and be asking that question and if all is clear

after you've got through withdrawal and you've got past the first 90 minutes after waking up and you tell me now in this more caffeine naive state in the first few hours i feel rest i feel refreshed i feel restored by my sleep then that's great we don't need to be concerned about your

sleep so that's the second reason i like it because it gives you the opportunity to test out whether or not your sleep is of good quality or not i should also note by the way that i mentioned i've changed my mind on caffeine and its use and this comes back to i just raised it because you had said

i made this suggestion and it wasn't binary it wasn't dictatorial you don't have to do it i wasn't saying that everyone needs to do it and in fact even i will you know tweak my schedule if i'm doing one thing in the morning i will take on board caffeine fairly soon if i'm not i will hold off

i came out the gate when i first published a book and it and i was very dictatorial about it i was very monos i was very binary you know it was sleep is absolute and it's it has to be this way and no other way i was not in favor of caffeine and i was telling people about the dangers and there

are dangers to your sleep and we can speak about those but it was a little bit too heavy handed i've changed my mind for at least two reasons first that's not the way society works or people live so there's no amount just like technology and saying leave your phone outside of the room

for two hours before bed and don't check it for the first four hours that that genius out the bottle so the reason i have changed my mind on caffeine is because if you look at the data on on caffeine it's stunning for health it on almost every metric that we can measure

drinking some degree of caffeine is beneficial now there is a new it there is a u-shape function to this which is once you get past sort of three or four cups of coffee then you start to go in the downward direction and things aren't so great the contradiction however was that i was telling

people caffeine not good for your sleep and sleep by the way is wonderful for health it transacts all of these benefits that we have and will discuss in this series but then you compare that relative to caffeine and caffeine transacts many of the same health benefits so how can you explain

that mr. sleep scientist well if you look the the data is very clear it's not the caffeine that's the benefit most people take on board caffeine by way of a cup of coffee and the coffee bean is packed full not just of caffeine it contains a whopping dose of antioxidants and because of our

deficient western diets were so absent of these antioxidants that the humble cup of coffee has been asked to carry the huckily in weight of our antioxidant needs on its shoulders so no wonder it by itself carries such a strong health signal because it's providing you with this wonderful

dose of antioxidants in addition to caffeine case in point if you look at decaffeinated coffee you still get the antioxidants but now you don't get the caffeine and low and behold you get many of the same health benefits it's not the caffeine it's the coffee itself so I think that is a perfectly

good reason to justify caffeine but again just like naps the dose and the timing make the poison if you're not someone who's sensitive to caffeine then having a couple of cups of caffeine and trying to step away from the use of caffeine I would argue somewhere between 10 to 12 hours before

you expect to go to bed depending on your sensitivity and it is different across people and we know that it's genetic there is a specific what we call polymorphism which just means a variation in a particular gene and if you look at variations in that it will predict whether you are someone who

is very sensitive to caffeine or not very sensitive to caffeine and it comes down to how quickly you can essentially metabolically remove that caffeine from the system so if you know that you're a very sensitive person I would probably argue try to stay clear maybe 12 to 14 hours if you're someone

who is not as sensitive then you could maybe go to eight hours the dangerous for people who say look I'm one of those people who is you know really just not sensitive to caffeine at all and I can have an espresso with dinner and I fall asleep fine I stay asleep fine so it's really not a problem

for me I would say that that that may be true but the inherent danger here is that when we've done these studies if I give you a dose of let's say 200 300 400 milligrams of caffeine in the hours before bed which would be a large you know strong cup of coffee or you know to espresso with dinner

some people can fall asleep and some people stay asleep but the amount of deep sleep that they have is compromised in fact it can drop your deep sleep by up to 20% now the danger is that you wake up in the morning and there is no signals in your sleep that said you had problematic sleep because

you're not aware of how much deep sleep that you had that's the reason that I think you know sleep trackers can be helpful in some ways but you then wake up and you don't feel as refreshed and restored but you don't remember having a hard time falling asleep or staying asleep but now you

find yourself reaching for three cups of coffee to wake up in the morning rather than the standard two and so goes the vicious cycle so and also you see an interesting interrelationship we did a recent study we just published in Wall Street traders it's not just caffeine use it's also about

alcohol use in the evening that people who over-medicate with caffeine during the day they then need something to bring them down at night and the principal depressant agent and depressant not in the sense of psychiatric depression but in the sense of brain neural activity depression

is alcohol so you get this classic cycle of uppers and downers I need my uppers during the morning my caffeine and I need my downers at night to low me into sleep and it's this really interesting trade-off which we we saw in these Wall Street traders so coming back to the notion of caffeine

though I am favorable of it in terms of its health benefits I think it's very very clear just be mindful of the dose and be mindful of the timing dose try to not exceed about three cups of coffee timing understand your sensitivity there are certain genetic tests if you really want to get

nerdy that will tell you if you have this sensitivity or not but you will probably know it and therefore just say okay I'm not that sensitive I could probably go eight hours or as close eight hours before sleep or ten hours if you're very sensitive 14 15 hours and keep it to one cup

so those are the ways that I would see moderating caffeine and changing my my mind on caffeine which just comes back to your point where you were saying okay I made this recommendation about caffeine I want to make sure I modify that so people don't get confused I certainly

needed to make a modification to my stance on caffeine so thank you for letting me say that which is a long winded way of getting around it but does that help that does help very much thank you for that addendum to the legislature okay so you told us about the power nap

and you've told us about the caffeine nap the so-called napa chino yeah what are some other types of naps that can be beneficial for sleep wake cycles and alertness so you can think about the caffeine nap is trying to amplify it sort of a nap plus as it were but two questions the study

that comes to mind there was a really int investigation hirk yulean in its study design from a great sleep research group out in japan and they asked okay the nap is good the caffeine nap maybe a little bit better but can we go further and so they designed a series of studies they had five

different experimental groups and they tried to basically create a stack a stacking system they had across the five groups there was a no nap group that's the control then there was a nap group then there was a nap plus caffeine group then there was a nap plus cold face and cold

hand washing immediately after you wake up i'll come back to explain why that we think that works and then the final group was a group that was a nap plus bright light and again thank you me offering this is the general public to you andry hubeman for your light revolution so it was

bright light at two thousand looks immediately afterwards so they had five groups again there was no nap group nap group nap plus caffeine nap plus cold hands and face washing nap plus immediate bright light the cold hands and face washing is interesting i told you before that there was this

three-part story to to the sleep wake equation that you need to warm up to cool down to fall asleep stay cool to stay asleep warm up to wake up and i'm saying warm up to wake up but use cold water on your face and your hands don't forget that warming up when i say it in the morning is

warming up at the central core of your body you reverse engineer what you did in the evening i said warm up to cool down to fall asleep so you warm up the periphery to release the blood from the core and you cool down well the reason that they use cold hand and face washing was because

that's this vascular surface it's the place where we can modulate temperature quite quickly the cold water on the face and the hands therefore caused phasoconstriction the vessels and the capillaries there they all scrunched up and they forced the blood back down into the core of

the body so the core body temperature increased a little bit now you also get a bit of an adrenaline shot when you're splashing very cold water on your hands in your face or the sum of that too but that's the justification so what they find firstly they were measuring different aspects of your

cognition and your mood and your sleepiness those were the outcome measures to assess how did these five different experimental groups change and you can imagine i mean this is i don't think i would ever take on a study where i'm doing five nap groups all within one study

it's bloody amazing so they did the no nap group and then compared to the no nap group the nap group got a wonderful benefit just as we described and they showed benefits in their alertness in their cognitive performance and also they showed a reduction in their sleepiness so point number one

on the scoreboard for a nap then they did the nap plus the caffeine and sure enough you got an added benefit to that which you already obtained from the nap now it was nowhere near a sizeable as the benefit from the nap so the addition of caffeine does give you some nice benefits and i've

used this before when i've worked with sort of professional athletes we do instigate these nap these caffeine naps when needed so it did give a nice benefit but then when they looked at the nap plus cold hand and face washing and the nap plus the bright light those also added something

to the nap benefit now they didn't do the sixth group which is really what i'm going to do some hand waving about which is the full stack full fat method where they said okay you're going to do nap plus caffeine plus cold hand and face washing plus bright light but if you were to put those

together my thought is that they're probably additive rather than simply just you know netting each other out which means that if you really want to not just do a nap or a nap plus which would be the the caffeine nap but the nap plus plus version you can lean into this study and the protocol

though would be you get into bed you have your espresso shot before you turn the light you swig it go down sit your alarm for 20 minutes you wake up the caffeine is kicking in you get over the inertia you go straight out cold hands cold face by way of cold water and then you get immediate

daylight for five to ten minutes outside and at that point you're really in a supercharged state so that's if you just because i know there's probably going to be some audience members who are willing to give this a try or who really want to optimize don't give me you know what is good give

me the extreme very best that's the only suggests that would have based on that data i love it and actually what you just described could easily be um translocated to the the period after uh waking from the nightly bow to sleep although one wouldn't ingest caffeine prior to waking up for obvious

reasons um but it would make good sense to me to wake up obviously get sunlight in one's eyes splash some cold water in one's face or hands or get cold shower cold plunge um caffeine or delay caffeine i mean it's essentially the same set of tools and i think it really um points to the fact

that circadian rhythm clearance of a denocene uh temperature modulation and of course the the way in which these interact um are really the the levers and knobs to to modulate awakefulness yeah it's it's so it there are i think we've gone over this notion of naps but there are ways that you can

try to manipulate the nap system still and there are ways that you can manipulate it even further but i like what you're saying because it just comes back to the fundamentals let's let's forego the the nap conversation just go back to the morning routine you're absolutely

right and think about the cold water and warm water my guess is that very few people when they go to bed they wash their face and their hands maybe they're probably not washing it with cold water before they go to bed correct they're going to be washing it with warm water why don't they do that and

they just say well why would a splash cold water on my face you know probably wakes me up you've never thought about why it wakes you up part of it is that you know at the shot of activation but the other part is thermoregulation and the opposite is what you want to do if anything

you want to be warming your hands and your feet that's exactly what you've always done you've always medicated your sleep onset by using warm water on your face in your hands several times during today's discussion we talked about polyphasic sleep

and the different types of polyphasic sleep that we covered are I wouldn't say conventional but they're conventional ish what are some of the more esoteric or let's call them high performance polyphasic strategies for sleep so we've spoken about polyphasic sleep in the natural way

idk which is during infancy and sleeping like a baby means that you're sleeping in a highly polyphasic way but probably around about the late 1990s 2000s with the emergence of the biohacker movement and the quantified self movement the started to become a lot of chatter online about

this notion of polyphasic sleep and here no longer oe infants were now adults but were engaging in a pattern that is highly polyphasic polyphasic sleep simply by definition again means that you're having multiple phases of sleep within 24 hour period and there are different strategies so the way

polyphasic sleep in adults works is that you take the 24 hour period and you think about it like a pie chart and then you start to slice that pie up into these quadrants when it comes to polyphasic sleep the goal is to put in certain multiple phases of sleep around the 24 hour clock rather than one

single phase but the thinness of those slices of the pie are very thin leaving large thick slices of wakefulness in between the notion that being that if you were to sort of just interspers little soupsons of sleep in terms of these little thin slices of sleep you can increase the amount of time that you're awake and you can increase all of the benefits of wake so if you look at the there is a website I think it's called the polyphasic society and there it's not a scientific society like the

you know psychological the American Association for Psychology or Medical American Medical Association or British Medical it's not one of those ratified certified scientific or medical it's just a society that lives online which is great and they make claims to suggest that polyphasic sleep

can improve aspects of your mood it can improve aspects of your productivity it can maybe even improve aspects of health I think sometimes there are claims that it can help with lifespan and there are a number of different schedules that they will describe to you and that you can find out that

of polyphasic sleep there is the first one that probably people have heard of is called the uberman schedule and by the way there is no hate at the start of that it is simply you I know it's not this man sitting across from me who has anything to do with this schedule and after we discuss the

data he will reassert that very same fact then there's something called the everyman schedule and then there is the triphasic schedule and there's lots of different other flavors of this the differences between them are in how you split up that pie chart and how much you assign to little thin slices

of sleep versus longer periods of wake and how many of those you insert but they all follow the same pattern if you look at the literature however it didn't begin with the biohacker movement the first description I can find in the human record comes from time magazine an issue in 1943

and they describe the protocol of at the time a fantastic very interesting designer a guy called Buckminster Fuller and he created a design principle and that design principle was called the Dimaxian principle the Dimaxian principle was principally used initially to build unique building

structures and it uses this notion of different sort of almost spokes that interconnect in a central hub that creates a self supporting structure the most obvious have you ever been to one of those geodesic domes and inside you go in it's like a botanical garden and it's all tropical despite you

being in a let's say you being in England in London it is beautifully tropical inside of that that structure that sort of lattice structure that comes in part from his design this was the Dimaxian principle and he scaled it to different things the Dimaxian car the Dimaxian house the

Dimaxian dome fascinating but he was no fan of sleep and he saw sleep as a rather significant waste of time when just like the rest of his Dimaxian principle he could be harnessing more efficiency out of the system with less structure and here less sleep structure inserted into his

twenty four hour period so he was the first one to describe his schedule and it was called the Dimaxian schedule of polyphasic sleep so it may have been a practice earlier in the record but that's the earliest one I can find so let's come back to the claims of polyphasic sleep that it could

improve let's say your mood or your cognition or your productivity or your health the a group of scientists at Harvard some of my old colleagues from Harvard they looked at all of the literature on all of the steas that were polyphasic like or testing this claim and the first thing that they

found was to their claims of improved cognition productivity mood as well as health they found no supportive evidence that polyphasic sleep was helpful then they turned the tables and they said well could it be hurtful and in fact that's exactly what they found firstly the total amount of sleep

that you get on any one of those schedules is decreased significantly now of course that's the goal the quality of sleep that you get though is miserable your sleep efficiency even when you're having these short periods of time especially during the waking hours is very poor it's not a type of

even short sleep that you would wish for third they found that it would reduce your REM sleep amounts so that was the first set of findings your sleep is no better if anything it's significantly worse and then they started to find that there were significant impairments in many of those things

impairments in cognition in judgment making and decision making impairments in mood and some aspects of impairments in metabolic health particularly glucose regulation so when it comes to polyphasic sleep sleeping like a baby if you're an adult seems to be a rather unwise piece of advice

now I mean it probably goes along with eating baby food drinking breast milk and and having somebody else clothing change you as an adult it's probably not advisable it doesn't seem to be at least supported by the data and again I want to be so careful here and you're very

careful too I'm not here to necessarily tell anyone absolutely how to live their life I'm just a scientist and all I can do is give you the information just as you do and then it's up to you to make the best decisions that you wish to make all I would say is that I would hope that as long as

you're not hurting yourself and harming your health and you're not hurting other people then and it makes you happy then I say whatever it is in life good luck I embrace it I always say do as do as you wish but know what you're doing and don't hurt yourself or anybody else can you get

me that t-shirt and I will wear it five days through Tuesday so here in this regard though I would say the evidence would suggest that maybe you're compromising your health and your wellness but that's your choice and I understand it so again no judgment to the question however of as long

as you're not hurting other people here I would say that there is a pause for caution because what we know is that when you're not getting sufficient sleep I described all of the health consequences in the first episode there's another danger here which is road traffic accidents and we describe these micro sleeps that happen and why car accidents that are caused by sleepiness can be so catastrophic there's a very interesting study that was done where they looked at people getting less than six

hours of sleep for several nights and they put them into a driving simulator and they asked what is the probability that you have a crash or an off-road event and sleeping less than six hours a night resulted in a 30% increase in you getting into a car crash now the AAA release some data showing that when you get down to five hours of sleep there is I think it's something like two to three times higher

likelihood of an accident based on real data and then when you are on four hours of sleep it was close to a ten times greater risk so in other words the less than the sleep that you get it's not a linear increase in your risk of a car accident it's an exponential increase so I bring this back to

polyphasic sleep because I don't know you know think about that 30% study let's not go to the extreme just less than six hours of sleep if this evening you called a taxi and it turns out two taxis turned up and outside of your door I said look one of these two you can choose either one of them

but I'll just tell you that one of these taxis has a 30% higher likelihood of getting in a crash relative to the other and it's this one on the right which would you like to pick or what would you like to put your wife and children in to send it's very obvious so I raised that question

just to be mindful no one would wish to cause harm on someone else to carry the harm of someone else by way of your own doing on your shoulders for the rest of your life is not one I would wish for and it's not one that you would wish for that's the only cautionary note but other than that I would

say you know sort of live life to the full well that brings us to the conclusion of yet another incredible voyage into the landscape of sleep most notably on the different phases monophasic bifasic and polyphasic sleep and naps and caffeine and all of their interactions these are such

important topics at the level of concepts the level of mechanisms and as you've also beautifully described at the level of protocols that is actionable tools that people can apply so thank you ever so much Matt for taking us even further along this voyage I'll just remind people

that episodes one and two of this series that Matt is sort of generously providing information about sleep for us are out and those can be accessed through links in the show no captions those fill in yet other mechanisms and aspects of sleep and I'm also particularly excited for the

fourth installment in this series coming up about the relationship between sleep memory and creativity so just incredibly important topics relevant to everybody I also just want to make note that I really appreciate you highlighting some of the developmental shifts that occur with sleep I

often get questions about you know sleep in children and babies and elderly adults as well as all the ages in between and you've just built this incredible tapestry of of information for people to think about and act upon should they choose so thank you Matt ever so much and I look forward to

episode four Andrew thank you it is such a privilege and it remains just my absolute delight to be here with you thank you thank you for joining me for today's episode with Dr. Matthew Walker to learn more about Dr. Walker's research and to learn more about his book and his social media

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