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

Welcome to the Hubertman Lab guest series where I and an expert guest discuss science and science based tools for everyday life.

I'm Andrew Hubertman and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine.

Today, March the third episode in our six 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 monophasic 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 bouts, 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 six episode series, today's third 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 Better Help. Better Help offers professional therapy with a licensed therapist carried out online.

I've been doing therapy for well over 30 years. Initially I had to do therapy against my will, but of course I continued to do it voluntarily over time, because I really believe that doing regular therapy with a quality therapist is one of the best things that we can do for our mental health.

Indeed, for many people, it's as beneficial as getting regular physical exercise. The great thing about Better Help is that it makes it very easy to find a therapist that's optimal for your needs.

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Again, that's BetterHelp.com-slash-huberman.

Today's episode is also brought to us by Element.

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As I've mentioned before on this podcast, I'm a big fan of salt. Now, I want to be clear, people who already consume a lot of salt or who have high blood pressure or who happen to consume a lot of processed foods that typically contain salt need to control their salt intake.

However, if you're somebody who eats pretty clean and you're somebody who exercises and you're drinking a lot of water, there's a decent chance that you could benefit from ingesting more electrolytes with your liquids.

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If you'd like to try Element, you can go to drinkElement spelled LMNT.com slash Huberman to claim a free Element Sample Pack with your purchase. Again, that's drinkElementLMNT.com slash Huberman.

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 Yoganidra and non-sleep deep 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, and can improve our memory.

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It includes a variety of different types of meditations of different duration, as well as things like Yoganidra, which place the brain and body into a sort of pseudo-sleep that allows you to emerge feeling incredibly mentally refreshed.

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If you'd like to try the Waking Up app, you can go to WakingUp.com slash Huberman and access a free 30-day trial.

Again, that's WakingUp.com slash Huberman.

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 is just one thing.

Most people sleep at night, some people also nap. A topic we'll also discuss today.

But it 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 monophasic, biphasic, polyphasic, unpack that.

Monophasic, obviously, just simply means a single phase, monophasic.

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.

Biphasic then means that within that 24-hour phase, you are having two bouts 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 see us to like nap in the afternoon?

And then we can speak about polyphasic sleep.

Polyphasic sleep, we in sleep science have been using for many years in the context of infancy.

Because there, as any new parents will know, infants do not just simply have a nice 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 polyphasic sleep.

The other term or the other application of that polyphasic 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 polyphasic.

And you are probably going through wake sleep phases every two hours.

Why do you do that? Why can't you just simply be born and sleep in a monophasic 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 polyphasic when you are first born

is because you're super chiasmatic nucleus.

And in another episode, we spoke about this 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, this 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, 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 polyphasic. 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 polyphasic sleep as infants to by-phasic sleep as kindergarten.

Could you describe that it was by-phasic patterns? I recall in kindergarten having nap time in the afternoon.

Yeah.

Put out these little mats and every kid would just go like, it's actually sounds really nice.

You know, wouldn't, and we'll speak about how some adults do this too.

But almost every kindergarten system that I've been quiet about around the world,

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, 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 monophasic 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 monophasic 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 monophasic, biophasic, polyphasic 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 as beautiful.

It is beautiful, but it turns out that it's probably the REM sleep state,

but the muscle 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,

those 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?

Does it sleep hanging upside down?

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 tone.

Couldn't it couldn't help but ask it?

It's genius.

The flora and the fauna.

Oh, I love it.

Don't get me stressed.

But especially the fauna enchants me that much.

So I don't want to draw us off, of course.

And 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, ver, unlike 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 damn, 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 impairments 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 synapses 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 bursts of electrical activity.

We will speak about the role of those sleep spindles in improving motor school 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 sort of that appropriate chronotype 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 were 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 most prndial dip, and it happens somewhere between the 1 to 4pm 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 and together 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 hunter gatherer tribes, the way that they also do not sleep in a similar manner to that which we do is the 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 sundown, 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 awake.

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 presumably likes to go to bed around 8 p.m. wake up around 4 a.m.

Most people here 4 a.m. and they go, oh goodness, you know, that's early. Sort of like the mighty jaco 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 an Instagram is a replete with images of his watch for 30 and people think goodness, that's early.

He was a guest on this podcast, spoken to him before, but he goes to bed pretty early. Most nights. So in some sense, you know, midnight for him or for somebody with a similar schedule is truly middle of the night.

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 byphasic 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 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 jaco 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 asleep 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 are, you've reduced your vulnerability down by 50% because mother nature injected the variability by way of genetics of chronotypes.

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.

So it's 24.2 or 24.4 and the idea in mind, the Jesso 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, you know, even at the equator across the year, there's subtle variations, but certainly as you move away from the equator.

These variations in, you know, 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 malleability to to matching the circadian rhythm to outside like dark rhythms.

Is that a decent parallel for what we're talking about here?

It's a beautiful demonstration that there is always some, it's almost wiggle room in how biology is programmed because some degree 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 yours was 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's 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, adolescents, et cetera, that our chronotype is somewhat mass 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 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 in someone who is in congrock 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.

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You'll get five free travel packs plus a year supply of vitamin D three K to again, that's drink AG one dot 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 leaving act. Monophasic byphasic and polyphasic. You give us a few more examples of different types of byphasic and polyphasic sleep. So coming back to byphasic sleep, I described one version once we are adults, which is the CS 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 byphasic, someone like me and neutral probably an hour and a half, two hours later still.

But there is a different version of byphasic 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 it's 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 and 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 decansean 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 siesta 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 forces 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.

But to me, it 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, second sleep has 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, I think 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.

And the second is, it wasn't a clear separation, it's just simply higher 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, you know, scaled up.

Did it happen for sleep second sleep? Yes, it did. Is there any strong evidence that 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 describe this byphasic pattern for people that were essentially experimentally restricted to the bed.

Is there something about being horizontal that makes us sleepy? There 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 body is 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 now'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 1 and 4 pm that many people try and combat with caffeine.

And 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 you know 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 you know caffeine is one of the few drugs that almost everybody takes just to quote unquote feel normal.

Yeah exactly. You know it's sort of I think sometimes you know sleep deprivation is is simply just the absence of caffeine and so it's a very interesting chemical which I have.

In truth change my mind on I'm happy to speak about why I've changed my mind but also some godrails to we'll we'll go there meanwhile I'll take a sip of my triple espresso here as we discuss as we discuss naps are 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 edge 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 once 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.

One group took a 90 minute sleep opportunity sort of focused right around that drop in alertness the other just remain to wake 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 low that will 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 crime in a whole list of facts at midday and then a whole list of facts new facts again at five p.m.

And I can ask what is the learning capacity of your brain at midday and at five p.m. 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 five p.m. was about 20% so that's certainly non trivial in terms of if you to save you know his and you 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 learning a 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 an app and then after a nap versus that same time in sort of mid day versus five p.m. another group did not nap and sure enough the group that did not nap by about five p.m.

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 nap 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 napt.

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 maybe thinking across the sounds good not to mention the basics which is your attention you concentrate on.

Your concentration your focus and your energy all 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.

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 a denocene and the longer that you're awake the more a denocene that builds up the more a denocene that builds up the sleepier you will feel after about 16 hours of being awake you should have lots of healthy sleepiness of a denocene in your brain.

So when you're asleep you're able to see your brain to put you asleep and keep you asleep and when we sleep we are able to clear that a denocene 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

so when you take a nap like a pressure valve on a steam cook up 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 devices 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.

So what we have to do 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 the day just takes the appetite edge of 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 do's and the don'ts of that if that sounds of somewhat interest.

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 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 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 is not a problem.

So this rather common phenomenon of waking up and feeling kind of groggy or even kind of grumpy and that the post nap face or we should call the post nap expression.

PNE. What's your PNE or do you wake up in the morning to somebody wake up and they're like that that face and then there's the like good morning you know and I think people that wake up with the good morning are particularly delightful unless you're of the post nap expression that is got to be.

The crumpled face and then you just you don't want to be around those you know absolutely yeah.

Yeah this probably relates to spirit animals and things like that somebody will wake up like a like a cheerful chipmunk and other people seem to wake up like my bulldog Costello words you know joules still in contact with the floor yeah so I'm PNE I'm trying to hold it together and not I've really 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.

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 is 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 knock up see 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 and 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 my concentration to be improved I want that sort of slight boost in brain energy where I know I can sustain myself for now along a period of time and I've got the motivation which is relieved in the morning.

Which is relieved in some ways how I like to think about energy as well I've got the motivation 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 a nap 50 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 in your basic reaction time maybe 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 so 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 human you don't get that almost sleep hangover so some people will say it's strange I nap maybe on that 45 minutes 50 minutes and I wake up and to be honest mad.

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.

Half awake half asleep when 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-rem then stage two non-rem and just before you get into the very deeper stages of non-rem three and four that started 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-rem sleep but you're not going so far into the cycle so deep into your non-rem that when you wake up after 20 minutes you're not in that what we call sleep inertia phase that sleep groggyness that sleep hang over 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 you're going to suffer.

So aim for about 20 minutes that's the dose the timing comes back to that which we described 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 p.m.

20 minute naps sometime between 3 p.m. 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

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is also something worth considering because I think many people listening to this or 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 yeah in other words

but simply should everyone think about having an early to mid afternoon protocol to reset their cognition in 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 to your 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

li these I'd love the phraseology that 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'm asked

procedure so put an I'm asked on make sure you block out noise earplugs you can use the 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

huge 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

grand deal drop you will know yourself everyone has fallen prey to it you know well it's usually around about 3 4 p.m. that I do start to feel this decline or it's around 1 p.m. 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 I'm 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

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 asleep 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 local deep non-ramp 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 bed will 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 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 their 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 24 hours so you're seeing 10 to 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 dingus 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 nap 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 be 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 reboost your power which it does and boost it back up it's because there was chuckles at the time prophylactic napping

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Again that's eight sleep dot com slash Huberman the naming of things fascinates me especially in the landscape of health and well being also and that 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 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 need you 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 coin 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 be great fun and I think very interesting for us to do that project to explore what are the brains activation states or deactivation states as the case maybe 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 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 byphasic sleep

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 napp within the day and the duration of that napp

what you told us a few moments ago suggests that I should be doing or anyone that's doing napps or entering these liminal states like NSTR might want to shift them a little bit earlier than the period in which they first become sleepy

to take that napp is that right I mean like so for instance should I do as my colleague and you know finish lunch 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 napp 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 napp late in the day you struggle to fall asleep you may not 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 napp 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

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 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 that and it just seemed 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 rigour 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 not immune to the vagaries of sleep I've had two bouts of insomnia throughout my life both of being 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 4 to 1

part REM sleep 4 parts non-REM in our 7 to 9 hours and I describe these changes in REM early in development I didn't mention 2 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 to not teenage as 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 cools 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 down scaling 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 organiser

has been doing over the past 13 years that's where we need to now place our bets

but as we get through into all the 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 memorabilites 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 are having when you are 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 are 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 lifespan 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 napuchino 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 magnetister and you'll explain I'm sure

and napping as you mentioned before removes some of the sleep pressure aka 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

so what's the story with caffeine how does it work to make us feel more alert and what is the rationale for the napuchino

the napuchino 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 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 chairs 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

and I'm just going to take a quick espresso shot and you get that you 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 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 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 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 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 a lense it's really not that though

or when you say placebo I also wonder whether it's possibly a conditioned effect

you know it's like a Pavlovian thing because the smell of the coffee that tastes

to the coffee the home of the machine you are walking into the cafe

to and ordering it from the barista also creates an anticipatory arousal

like the the alertness is coming and in that anticipation there's its own form of alertness

I think 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 their caffeine warm

either it's tea or it's coffee or it's perhaps something else that Andrew human would drink

but many people... Yerbamata

since I was five years old I don't I don't know if I should have been drinking

caffeinated Yerbamata so young maybe even four years old there's a photo of me

on my grandfather's lap drinking out of the Montaigord half my family's Argentine

and so I was caffeinated from a young age this brain developed in a caffeinated mill you

this explains so much about what I've known of you over these... no I'm kidding you

so we need to speak like that 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

deep 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 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

I love it, the napachino

maybe I'll give it a try

this is the first time I've ever heard the rationale

and 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

can exercise clear a dentisine, can cold shower clear a dentisine

and 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 member of the National Academy of Sciences

a brilliant guy he said you know a drug is a substance that when injected into an animal or a human

produces a scientific publication

meaning 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 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

which is again it's heuristic 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 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 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

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 in the afternoon

and all of which dominoes to as we'll talk about more in the series to better sleep at night

because 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 at 5.45 am somebody is asleep

and adenosine is still being cleared away because they're asleep

and they wake up boom does adenosine clearance immediately stop

well for people who have that crumpled face, groginess

and they wake up at 5.45 maybe even by way of alarm although we don't suggest that

and they stagger into the kitchen or nearly they make their cup of coffee

but they're in a pseudo sleep state

so it stands to reason that they're still clearing adenosine

now if they are to drink caffeine right away then as you pointed out going to block those adenosine

receptors and there's going to be a continued build up of adenosine as opposed to a clearance of adenosine

so this was 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 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 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

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'm looking back on my night

I'm awake now after my caffeine and now is the important part of that sense

and so 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

and I'm 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 you 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

and 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-shaped 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 we'll 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 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 herculean 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 8 hours

the danger is for people who say

I'm one of those people who is 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 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 strong cup of coffee

or two 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 percent

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 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 stand two and so goes the vicious cycle

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 saw in the 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 to eight hours before sleep

or ten hours if you're very sensitive

fourteen, fifteen hours and keep it to one cup

so those are the ways that I would see moderating caffeine

and changing my mind on caffeine

which just comes back to your point where you were saying

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 a little bit?

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 nepachino

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

just trying to amplify it as sort of a nap plus as it were

but two questions

the study that comes to mind there was a really int investigation

Herculean in its study design

from a great sleep research group out in Japan

and they asked okay the nap is good

caffeine nap may be 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-nep 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

Andrew Huberman for your light revolution

so it was bright light at 2000 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 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 a vasoconstriction

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 and your face

so there's some of that too

but that's the justification

so what they find

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 as sizable 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 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 facewashing

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 facewashing 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 caffeine nap

but the nap plus plus version

you can lean into this study

and the protocol there

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 this

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

translocated to the

the period after

waking from the nightly bow

to sleep although

one wouldn't ingest caffeine

prior to waking up for obvious reasons

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

caffeine or delay caffeine

I mean it's essentially the same set of tools

and I think it really

points to the fact that

clearance of a denocene

temperature modulation

and of course the way in which these interact

are really the levers and knobs to

to modulate awakefulness

yeah it's so it

there are I think we've gone over this notion of naps

but there are always that you can try to

manipulate the naps 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 forgo

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

they're going to be washing it with warm water

why don't they do that and they just say

it's a splash of cold water from a face

you know probably wakes me up

you know thought about why it wakes you up

part of it is that you know

at the shot of

activation but the other part is

themoregulation and the opposite is what you want to do

if anything you want to be warming your hands

and your feet and that's exactly what you've always done

you've always medicated your sleep onset

by using warm water on your face and 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 what's

called 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

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-set 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

interspersed little soups-ons 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

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

H 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

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

in 1943

and they describe the protocol

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

and it's a very important

structure that is

the most obvious

structure that is

the most obvious

have you ever been to one of those

geodesic domes

inside you go in

botanical garden

it's all tropical

in England

and it's beautifully tropical inside of the

that structure

that sort of lattice structure

and it's a very

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

24-hour period

so he was the first one to

have a very

very significant

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

these that were

polyphasic

like or testing this claim

and the first thing that they found

was to the 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

in the record

so that's the most important

and the most important

what is the probability

that you have

a crash or an off-road event

and sleeping less than

sleeping less than

[수면 최적화와 낮잠의 과학: 매튜 워커 박사와의 대담]-[GUEST SERIES | Dr. Matt Walker: How to Structure Your Sleep, Use Naps & Time Caffeine]

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수면의 구조와 생애주기에 따른 변화

REM 수면과 뇌 발달의 상관관계

낮잠의 명암: 효과와 주의사항

카페인과 '냅푸치노(Nap-a-ccino)'

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