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

[Music]

welcome to the hubman lab guest Series

where I and an expert guest discuss

science and science-based tools for

everyday

life I'm Andrew huberman and I'm a

professor of neurobiology and

Opthalmology at Stanford School of

Medicine today's episode marks the first

in our six episode series all about

sleep our expert guest for this series

is Dr Matthew Walker professor of

neuroscience and psychology and the

director of the center for Sleep science

at the University of California Berkeley

he is also the author of the bestselling

book why we sleep during the course of

the six episode series for which we

release one episode per week starting

with this episode one we cover

essentially all aspects of sleep and

provide numerous practical tools to

improve your sleep for instance we

discuss the biology of sleep including

the different sleep stages as well as

why sleep is so important for our mental

and physical health we also talk about

how sleep regulates things like

emotionality and learning and

neuroplasticity that is your brain

ability to change in response to

experience and we discuss the various

things that you can do to improve your

sleep everything from how to time

lighting temperature exercise eating and

the various things that can impact sleep

both positively and negatively such as

alcohol cannabis and various supplements

and drugs that have been shown to

improve sleep we also talk about naps

dreaming and the role of dreams and

lucid dreaming which is when you dream

and you are aware that you are dreaming

in today's episode one we specifically

focus on on why sleep is so important

and what happens when we do not get

enough sleep or enough quality sleep we

also talk about the various sleep stages

and we also talk about a very specific

formula that everyone should know for

themselves called qqr T which is an

acronym that stands for Quality quantity

regularity and timing of sleep four

factors which today you'll learn how to

identify specifically for you what your

optimal qqr is and then to apply that in

order to get the best possible night's

sleep which of course equates to the

best possible level of focus and

alertness throughout your days both Dr

Walker and I are very excited to share

the material in the six episode series

with all of you and as we March into

today's episode one I'm sure it will

both provide a ton of excellent

practical learning for all of you as

well as spark many questions that are

sure to be answered in the subsequent

episodes of this series before we begin

I'd like to emphasize that this podcast

is separate from my teaching and

research roles at Stanford it is however

part of my desire and effort to bring

zero cost to Consumer information about

science and science related tools to the

general public in keeping with that

theme I'd like to thank the sponsors of

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huberman and now for my conversation

with Dr Dr Matthew Walker Dr Matt Walker

welcome Dr hubman it's an absolute

privilege and a delight to be back

that's right you've been on here before

but I have during this episode in this

series we are going to go a lot deeper

by the way you look very well rested

thank you very much I actually slept

pretty well last night um despite it

being a foreign location um same time

zone that helps just astronomically

amazing well rather than ask you what a

great night's sleep is for you because

I'm pretty sure you're going to tell us

that there's uh some individual

differences that people need to pay

attention to in terms of what is quote

unquote optimal sleep let's start off

with the

basics what is sleep so sleep I think in

some ways you can Define as at least in

humans and in fact in all mamalian

species is broadly separated into two

main types of sleep on the one hand we

have something that many people will

have heard of called nonrapid ey

movement sleep or non-rem sleep for

short and non-rem sleep has been further

subdivided into four separate stages and

they are unimaginatively called stages

one through four increasing in their

depth of sleep so stages three and four

that that's the really deep sleep that

we can speak about and I should explain

a little bit at some point what happens

during that state with in the brain it's

stunning it's astonishing so you've got

stages one and two light non-rm sleep

when you sort of look at your sleep

trackers and it has light nonrem deep

nonrem and then REM stages one and two

that's light nonr stages three and four

that's deep nonr and that's non-r

encapsulated on the other hand we have

rapid eye movement sleep or remm sleep

and it's named not after the um popular

Michael styp band of the 1990s but

because of these bizarre horizontal

shuttling eye movements that occur

during this stage of sleep hence the

rapid eye movements and REM sleep is the

depending on your definition and we'll

probably come to this in in uh later

episodes It's the principal stage in

which we dream but if your definition is

quite loose which is any reported mental

activity when I wake you up or when you

wake up then it turns out that we dream

in almost every stage of sleep but I'll

describe REM sleep from here on in as

perhaps you dream sleep and I'll make

that faux part so you've got these two

types of sleep non-rem and REM

sleep they will then play out in this

beautiful battle for brain domination

throughout the night and that cerebral

war is going to be won and lost on

average for the average adult every 90

minutes and then it's going to be

replayed every 90 minutes and that

creates the standard cycling

architecture of sleep so whoever is

listening to this when your head hits

the pillow tonight what will happen

you'll start to go down into the light

stages of non-rm then you'll go down

into the deeper stages of non-rm sleep

and you'll stay there and after about 45

50 60 Minutes you'll start to rise back

up again and then you'll pop up and

you'll have a short REM sleep period and

then back down you go again down into

non-rem sleep and up into REM sleep and

as I said you cycle through that on

average about 90 minutes but I'll come

back to that what's interesting however

is the ratio of non-rem to REM within

your 90minut cycle is not stable and

what I mean is as you move across the

night the the the domination of those

two types of sleep within the 90-minute

cycle changes such that in the first

half of the night the majority of those

90 minutes Cycles are comprised of lots

of deep non-rem sleep but very little

REM sleep but as we push through to the

second half of the night now that ratio

balance that seesaw balance shifts over

and instead we have much more rapid ey

movement sleep and very little deep

sleep so when people think about okay I

just go to sleep I lose Consciousness my

brain is still firstly nothing further

from the truth could be the case in in

terms of your sleep second your sleep

has a very specific pattern that has

consequences to real life so let's say

that you're someone who normally gives

yourself an8 hour sleep opportunity in

bed but the next morning based on what

I've just told you you say okay well I

want to I'm going to get a jump start on

the day or I've got an early morning

flight so I'm just going to come up with

numbers here I'm not suggesting that

this is the ideal sleep schedule by any

means but just to make the numbers

simple let's say someone normally goes

to bed at midnight and wakes up at 8: so

there's their 8h hour opportunity but

today they're going to wake up at 6:00

a.m. rather than 8:00 a.m. to get this

push on the day how much sleep have they

lost well technically they've lost 2

hours of the 8 hour so they've lost

25% but that's not entirely true they

may have lost 25% of their total sleep

but because of the strange structure of

deep sleep first and then REM sleep

later they may have lost 60 70 maybe 80%

of their REM sleep so I only make this

point because understanding how sleep is

structured can have

consequences I will come back to the 90

minutes though it's fascinating we've

often and some people probably have

heard this before it's a 90minut cycle

well there's huge variability some

people can have a sleep cycle on average

that's maybe 75 minutes others 120

Minutes is it consistent within an

individual it is relatively stable

within an individual so I would say that

the size of the difference from one

individual to the next is much bigger

than the size of the difference within

an individual from one night to the next

to the next not unlike a healthy

menstrual cycle in a woman which can

range from a short is you know 24 days

to 31 days and still be considered a

healthy cycle that regular but and it

will change across the lifespan of

course but for a good number of years

it's going to be pretty consistent

within a given woman uh and yet Between

Women it can vary quite a bit immensely

yeah and what's also interesting is that

speaking about um some sex specific

things there are sex differences so on

average men if you look at them will

have a sleep cycle that's about 15 to 20

minutes longer than women which on a

90-minute average is actually quite a

lot and I bring this point up because

you may have seen some of those sort of

claims or devices out there well firstly

probably on social media and people send

me these things and say is this true

which is you really have to structure

your wakeup time at these very distinct

90minut on the clock when the clock

strikes the 90-minute midnight you know

that's when you have to be waking up and

you should set your alarm right these

the the rational you'll tell me that

it's wrong presumably but the rationale

of those devices is that one would be

better off waking up at the end of a

90-minute cycle as opposed to in the

middle of a 90-minute

cycle even if it means getting less

total sleep because the argument is that

waking up at the end of a 90-minute

cycle allows one to be more alert upon

waking right that there's something

uniquely special about the completion of

a 90-minute cycle that will have you Ed

out of sleep feeling like an Energizer

Bunny kind of that's some of the claims

that they and if I were to ask now true

or false false so sleep for as much as

you possibly can sleep don't terminate

that sleep artificially on the basis of

anyone telling you that there is this

kind of Da Vinci Code magic 90 minutes

that's unfortunately not true and I you

know I've been guilty of saying you know

it's a 90minut cycle and repeating that

so if I didn't know any better I would

believe that so I'm not trying to you

know chasti anyone I'm just simply

saying be aware of that and don't worry

don't stress about this unique 90-minute

cycle and there's some products out

there that say they're going to time you

on your 90-minute cycle and wake you up

I would probably stay a little bit clear

of some of those what about going back

to sleep you said to get um as much

sleep as possible if I get six hours of

sleep and then wake up and I feel like I

could go back to sleep would I be better

off going back to sleep provided that my

work schedule allows for that or um is

it the case that after you've gotten a

certain amount of sleep that's a good

idea to get up and and go I would say

that if you feel as though there's still

more sleep in you MH there is

or I love that this has become

biographical instantly it's going to be

a good episode when that happens I would

say hold tight stay in bed with an

asterisk that I'll come back to and see

if you can get get back to sleep and we

can speak about different ways of

helping you do that

but the reason I put a a slight asterisk

there is the following if you're then in

bed for the next 45 50 minutes wide

awake the danger and it doesn't happen

to everyone but the danger is that you

start to associate this thing called

your bed with this thing called

wakefulness and not sleep and one of the

things that we do in cognitive

behavioral th y for insomnia is we try

to prevent you from spending long

periods of time awake and I would say

it's probably about a 25 minute rule of

thumb it's not a rule it's a rule of

thumb if after about 25 minutes you just

can't seem to catch it and this is

happening frequently I would just be

mindful of you then starting to build a

bonded Association in your brain that

your bed is also the place of being

awake the analogy would

be you would never sit at the dinner

table waiting to get hungry so why would

you lie in bed waiting to get sleepy and

the answer is that you you shouldn't and

so we need to break that Association now

there's nothing stopping you however

from saying there's still sleep in me I

know that there is so I'm just going to

get out of bed go to a different room

I'm just going to read a book listen to

a podcast and then only when I feel

sleepy I'm going to go back to bed

because my schedule allows for it that's

the best way I would tell you if you

still think the sleep that on the table

to try and get it back that's immensely

valuable uh knowing that there's sort of

a conditioned Place effect of of being

awake in bed um I must say I get pretty

good sleep most of the time there have

been phases of life including recently

where sleep has been challenging and I

notice as I head toward the bed to go to

sleep recently the words in my mind are

here's the battle Gra like it's going to

be a night of going to sleep waking up

going to sleep waking up we'll get to

this business of of continuity of sleep

a little bit later so we don't have to

go into that now but I I should also

note by the way that for some people

when I speak with them they will and

it's just because you you mention it

it's beautiful they will be saying I I'm

so surprised because I am watching

television and I'm falling asleep on the

couch and then I get into bed and I'm

wide awake and I don't know why and

that's because in part you've built this

this connection in your brain and it's

and when you go into the bedroom that's

what we try to do with cognitive

behavioral therapy for insomnia you

spoke about it as a Battleground that

it's almost this adversarial thing which

in some ways infers that at that point

you feel as though your sleep controls

you and it is a miserable feeling and

gradually over time what we would do is

work with someone and at that point now

you control your sleep your sleep

doesn't control you and that is so your

freedom when you get it but sorry I

interrupted you oh no uh I interrupted

you but um thank you yeah I've prided

myself my whole life on being able to

sleep anytime anywhere uh I learned it

from my Bulldog Costello or maybe that's

what brought us together because he

certainly had that I'm so sad he's not

here around anymore with us CU I would

have loved to he feels like he is the

best sleep Ambassador if there's a post

to child for good sleep well he's here

in spirit um sleeping um so this is

interesting and I think it's important

for people to hear if if you can't fall

asleep or if you wake up in the middle

of the night and you can't fall back

asleep pretty quickly after about 20

minutes or so probably best to get out

of bed um so these 90 minutu is

cycles that include different types of

sleep um prompt me to ask if you were to

describe the basic characteristics of

each of those four stages of sleep and

especially the deeper stages three and

four and REM sleep not just at the level

of Rapid Eye movements during REM sleep

but in terms of the types of Dreams or

the characteristics of of kind of bodily

State and you know maybe you just flesh

out the physiology and neurochemistry

and you know touch on kind of the the uh

dream features associated with each of

these uh different stages of sleep this

just gets so exciting to me and even now

when I go into the lab where I look at

sleep traces um from my sleep center it

I'm am still in awe in bewildered awe of

what the brain does so as we start to

fall into those lighter stages of sleep

once you get past stage one sleep which

is sort of almost the shallows where

you're just wading out um then you go

into stage two sleep and one of the

Hallmarks of stage two non-rem sleep or

something called sleep

spindles and the way that we measure

sleep in a laboratory by the way is that

we place you look like a spaghetti

monster you've got all of these

electrodes on your head you've got

things above your eyes and you've got

things on your body and we're

essentially measuring three main signals

electrical brain activity we're

measuring muscle activity and we're

measuring eye movement activity and I'll

explain why those three things are

necessary for me to know are you awake

are you in sleep and if you're in sleep

which stage of sleep you're in so going

into that stage two non-rem sleep we've

got these sleep spindles and at that

point I'm looking at the electrical

signals from your brain what we call the

EEG or the electri

inogram and these sleep spindles are

these beautiful short synchronous bursts

of electrical activity and they last for

about a second to two seconds maybe a

little

longer and they are bursting at a what

we call a frequency of somewhere between

12 to 15 Hertz and what that means is

that these brain waves are going up and

down 12 to 15 times per second that's

what our measure is 12 to 15 Hertz

and then you go back and your brain at

that point has started to slow down now

when we're awake your brain wave

activity can be going up and down maybe

20 30 40 times per second it's very fast

and frenetic it's actually very chaotic

electrical brain activity but as we're

going into these lighter stages of sleep

then the brain starts to slow down and

at that point in stage two nonrem it's

maybe going up and down just four to

eight times per second so a huge

deceleration in terms of brain wave

activity but occasionally you'll get

these s of it's

going and then you'll get these

beautiful bursts of these sleep spindles

um I actually did I I've never published

it publicly or um we did a project

called the sonification of sleep and we

took these electrical signals and then

we turned them into sound waves and you

can actually hear this beautiful sort of

this it's almost this beautiful

throbbing of a Slowdown in your brain

and then you'll hear these spindles

almost sounds like that beautiful

delicious rolling R in Hindi so this

it's just wonderful I'm not sure I can

do that R how's it

go yeah not too bad not not too bad I

mean we're ering on the side of feline

but that's okay Andrew um so so coming

back to I'm so sorry um coming back to

sleep we've gone into light stage two as

I'm trying to desperately hold it

together um and we're going down into

deeper non-rm sleep now something

spectacular happens and this is where I

just almost lose it every time I see it

the brain now goes back down and it's

speed of of oscillation of going up and

down is maybe just one or two times per

second it's incredibly slow and this is

whole brain activity or localized

activity this is so we'll come on to

this first the way we would measure it

is just from these electrodes which are

measuring hundreds of thousands of brain

cells underneath them so a good analogy

would be let's say you're at a a

football stadium and it's Stanford

playing Berkeley in in American football

and what we've got is a single

microphone dangling over the middle of

the stadium and that microphone is

picking up the summed voices of the 60

70,000 people underneath it's the same

thing with when we place an electrode on

your head you're measure measuring the

summed activity of hundreds of thousands

of neurons underneath but we've now

started to use maybe 100 200 electrodes

on your head and we can pick these up in

local territories of your brain but that

beautiful powerful slow brain waves um

that were getting during deep non-rm

stages three and four it's not just slow

activity you would think okay that's

that that sounds like the brain is

dormant no no no the brain at that point

the size of the w waves is almost

quadruple maybe 10x the size of the

brain waves when you are awake why is

that meaning that the brain waves are

going up and down very slowly but the

size of them which is what we call the

amplitude that is now huge it's epic so

think about it you're on the beach and

when you're awake the waves are coming

in very very quickly but they're small

waves and they're coming in in a random

fashion but deep slow wave sleep are

these kind of Epic things that would

happen in Hawaii where you just get

these 20 30 foot waves and they're

coming in very slowly but they are

epically big that is deep slow wave

sleep and then what happens is riding on

top of those big slow waves are these

sleep spindles they just keep coming so

according to the sort of the Sleep

sonification project what you would hear

now these slow waves would

be that that's the slow wave and the

Sleep

spindle what is it that happens in your

brain though to your question to produce

these slow waves well let's go back to

the football stadium analogy there

before the game that's wakefulness

everyone is having a different

conversation in a different part of the

stadium and and you just get this kind

of incoherent sort of blabber that's

going on that's wake your brain is doing

different things at different sort of

locations of the brain processing

different information at different

moments in time and that's the fast

frenetic activity of wakefulness when

you go into deep sleep all of a sudden

for reasons that we still don't quite

understand hundreds of thousands of

brain cells in your cortex all decide to

unite in their singular voice of firing

and they all fire together and they all

go silent together they all fire

together they all go silent together and

that's what's producing these huge big

powerful waves so the analogy in the

football stadium would be at this point

now and I'll I'll come across to um to

to your University Stanford is is is

winning and the the crowd is buoyant and

all of a sudden the Stamford crowd is

singing Berkeley sucks Burkle sucks and

they're all uniting the whole stadium

cries out at the same time and then goes

silent at the same time it's an epic

display of coordinated neural activity

in a way that we don't see in any other

brain State it's phenomenal it's just in

all you answered the question I was

going to ask which

is does the pattern of brain activity

that you just described occur in similar

or identical form during any waking

States and I think you just said the

answer is no meaning if I understand

correctly this is a very very

specialized brain State unique to sleep

unique to a specific portion of sleep

and that begs the question what is it

doing so it turns out that all of these

stages that we'll describe different

stages of sleep do different things for

your brain and your body at different

times of night and it's very

understandable that people sort of in

the public will come over to me and say

you know how do I get more deep sleep or

how do I get more REM sleep and my

question back to them firstly is why do

you want more REM sleep and they'll say

well isn't that the good stuff and I

will say well it turns out that they're

all important you need all of them but

we can come on to let let I'll speak

about non-rem sleep functions first and

then I can probably I should unpack REM

sleep um and then explain its functions

but as an overview what we know is that

during deep sleep first you switch over

in terms of your body's nervous system

to what we call the parasympathetic

nervous system that you've spoke spoken

about a lot before which is this kind of

very quiescent calming state of your

body's nervous system the sympathetic

nervous system which is very poorly

named because it's anything but

sympathetic it's very aggravating and

activating and um when we're awake that

seems to be somewhat more dominant

depending on what state you're in but in

sleep especially in deep Sleep you shift

over into this very strong

parasympathetic quiescent calm State and

that instigates together with other

things

um and we've demonstrated by the way

that we published a paper probably about

a year and a half ago that these slow

waves and these sleep spindles and the

cordination of them how well that

they're coordinated seems to instigate a

signal down into your body's what we

call the autonomic nervous system which

carries both the sympathetic and the

sympathetic nervous system inside of it

and forces you over into a

parasympathetic state so these brain

waves one of the things that they seem

to be doing is transacting a message to

your body's nervous system to say calm

down quiet down what then happens

firstly what we see is your

cardiovascular system ramps down deep

sleep you could argue is almost the very

best form of blood pressure medication

that you could ever wish for it's

beautiful then something happens within

your immune system we're start starting

to unpack this but we still don't quite

know why these pulsing deep slow brain

wavves seem to be a trigger for

instigating two things for your immune

system firstly it stimulates the

restocking of the Weaponry in your

immune Arsenal so that you wake up the

next day and you are a more robust

immune individual so these are things

like tea cells natural killer cells that

sort correct all of that good stuff but

what's also interesting there's a more

recent discovery um it's not just that

your body has um put back all of this

Armory in place and in fact Amplified it

but your body

sensitivity to those immune factors has

also increased so you've restocked the

the weaponry and you've made your body

more sensitive to those immune signals

and that's why we will see in probably

later discussions your immune system can

start to become you know really markedly

impaired when you're not getting enough

sleep so that's a second benefit of the

Deep Sleep um brain wave patterns the

third benefit that we've realized is

that it's very good at regulating your

metabolic system and specifically your

ability to control your blood sugar and

your blood glucose and if we selectively

deprive you of just deep sleep alone and

we can do this now very cleverly it's

not as though I see you going into deep

sleep and I go into your bedroom and I

wake you up and then you go back to

sleep and which is how we used to do it

sort of 10 years ago now we can use a

very clever method where we play

auditory tones to your brain but they

are of a level that will not wake you up

it's what's called a sub Awakening

threshold and we determine that and by

playing those tones it forces the brain

to resurface out of deep sleep so you

will still sleep a total 8 hours but I

will have selectively excised just your

deep sleep and when I do that sure

enough your blood sugar ability your

ability to control your blood sugar I

should say is impaired really quite

demonstrably and it's for at least two

reasons the initial thing is that your

pancreas when it sees this spike in

blood sugar it normally releases

something called insulin and that

insulin is a trigger to your body to say

start absorbing the blood sugar so we

don't get this toxic or we don't

maintain this toxic spike in blood sugar

your pancreas when you are underslept

and specifically when you're not getting

enough deep sleep does not release the

appropriate amount of insulin worse

still what we found is that's

selectively depriving you of Deep Sleep

means that what little insulin is

released the cells in your body become

less receptive to that insulin so you're

not releasing enough of this chemical to

say start absorbing blood sugar and the

cells that are they designed to do the

they stick a straw out into your

bloodstream and they suck up the blood

sugar they don't respond to the insulin

anymore so on both sides of the blood

sugar regulation equation you become

imper and then I can give you an example

upstairs in the brain one of the things

that we found and we'll discuss is that

deep sleep helps regulate your learning

in your memory functions it helps start

to move memories around in your brain

and protect them and shift them from

short term to long term deep sleep

however we've now discovered is critical

for drisking your Alzheimer's trajectory

it's during deep sleep when you have a

cleansing system in the brain that

starts washing away the toxic proteins

that build up by way of wakefulness and

two of those toxic components are

something that we call beta ameloid and

Tow protein which are fundamental

ingredients in the Alzheimer's disease

brain equation

so certainly I could then understand

based on that Litany of things that I've

just provided and those are only a few

of what deep sleep is doing you could

imagine that's the stuff that I want to

get and that's the thing that I need to

optim for not true because there is REM

sleep I'd like to take a brief break and

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huberman before you talk about REM sleep

um what about stages one and two of

sleep are those just um kind of the jog

into the into the Sprint that is uh deep

sleep stages three and four or if I were

to Stage the question I'm asking as an

experiment let's say I'm an

undergraduate or graduate student in

your lab and I say um can we do an

experiment where we selectively deprive

people of stage one and two sleep only

and and then of course the question

becomes what do you put in there instead

so there's a bunch of other experiments

that one would have to do but has that

experiment ever been done and if so uh

what is the consequence of being stage

one two deprived um as opposed to just

deep sleep deprived so just as you

already um elegantly demonstrated that

stage one selective deprivation is very

difficult because it's a denovo thing

you have to pass through to get to the

other stages of sleep is stage one the

stage of sleep that I and other people

have experienced many times where you're

falling asleep and um you start to have

a a dream perhaps about walking or

running and then you kick yourself away

that's right okay oh and I should have

explained what happens stage one I love

so as we're going into stage one

obviously our eyelids are closed but one

of the first signs that we know as we're

recording I told you we're recording the

electrical activity on the head with

these electrodes but I also said that

we're measuring IM movement activity and

as you're going into light stage one non

RAM for reasons that again we have no

idea why your eyeballs start to roll in

their sockets underneath your eyelids

that change that we can start to see we

call them Slow Rolling eye movements and

they are the Hallmark of you entering

sleep and if you are lucky enough to

have a partner you can see this you can

you know as they're falling asleep you

will see these bizarre now granted if

they wake up usually the relationship

has terminated very quickly because the

thing are you next time I'm on a plane

if the person next to me is sleeping I'm

going to be the guy kind of like you're

a mirror yeah no don't do that I'm the

only one who gets away with it cuz I'm a

card carrying sleep scientist and even

then yeah American Alliance sometimes

take some bridge but um so you get these

Slow Rolling eye movements and the brain

waves start to to sort of slow down

again but you mentioned something else

and they are called hypnogogic Jer and

as we're going into this first stage of

sleep I told you that the principal

stage in which we dream is rapid eye

movement sleep that's not exactly true

because everyone has had this experience

that just as you're drifting off you

start to have these little mini dreams

almost sort of diet or dreams light

lit and you you you can almost wake

yourself up based on the fracture point

of cognition and what I mean is you're

thinking okay so tomorrow uh I've got to

get to the studio I'm interviewing that

desperately annoying British guy M

Walker and then there was uh the

elephant in the room with a helicop to

the wings on its head and and you almost

just think it wakes you up because you

think wait wait sorry excuse me go back

rewind what just happened that's the

point at which you've transitioned over

into the what we call the hypnogogic

state where you can have these

hypnogogic dreams but you also get these

JS we don't fully understand what

happens but the what we do understand is

that as you're going into sleep you

start to lose different aspects of your

sensory perceptual apparatus not losing

the sense of where did I where did they

go and I can't find them but the the the

processing of those now many will remain

during sleep one of the things that

starts to degrade is what we call

proprioception and you've spoken about

this before which is knowing how your

body is sort of positioned in space so

it propri reception is fascinating as

you're walking with a colleague and

you're crossing over a street have you

ever had that feeling where you sort of

you step off the curb and you're

chatting and all of a sudden you have

one of those really ugly wobbles where

you can oh and it's because you had

calculated non-consciously and

computationally you understood where

your foot was in space you understood

the velocity force with which it was

descending down onto the road below you

you had miscalculated the distance and

your brain had expected your foot to hit

that that road at a certain time and it

did not it sends an error signal back up

your spinal cord and that's where you

get that yeah this happened to me um uh

just last weekend I was at the San

Francisco Zoo and periodically

throughout the landscape of the San

Francisco Zoo they have these kind of

squishy surfaces that are seamless with

the concrete around them I think this is

so kids can play on the the various

sculptures there and if they fall it's a

little bit more forgiving so I was just

walking across this thing talking to the

person to my left and I stepped on this

now rather squishy surface and all of a

sudden I'm like I don't know how to walk

across this thing and I'm you know I've

been walking a long a long period of my

life and I really had to pay attention

and then and then transition back onto

the concrete and could stop thinking

about it for a moment and you almost

then have to stop the conversation that

you were having because it takes over

and you switch from non-conscious

proceptive and you switch over so the

issue is that when you are lying there

awake in bed you sense the mattress

underneath you you sense the support

you're getting all of that feedback

signal that I was telling you was absent

when you in inappropriately calculated

the distance down onto the road all of

that is in place and your brain is

saying everything's fine but as we're

drifting off into sleep we start to lose

that proprioceptive feedback now

normally that loss of propri acceptive

feedback and sensation of what's going

on and where my body is is is is before

the loss of consciousness and so you

lose Consciousness and that's then

thereafter when the loss of propri

reception happens and you don't have

this sort of you know mental freak out

of of propri receptive break glass in

case of

emergency but sometimes the speed with

which those things happen changes and

you start to lose the propri receptive

sensation before you fully lose

Consciousness and at that point your

body says oh my goodness mattress has

just disappeared and I'm falling

got and that's where you can have these

these jugs that's that's our current

best theory I know we're going to talk a

lot about dreaming in a later episode of

the series but uh what you just told me

forces me to ask at this moment whether

or not in dreams where we sense we are

flying is that possible because of the

absence of proception we we're sort of

we're on the mattress or on whatever

surface we sleep on but according to the

brain there's uh we're suspended in

space is that right yeah so it's it it's

one possibility as to why we have those

experiences in some ways though it does

bring us on to REM sleep during REM

sleep and I'll explain what happens in

the brain but what you're talking about

is something that is even more unique

about REM sleep as we go into REM sleep

your brain paralyzes your body so you

are physically locked into the

incarceration of your

body why why would your brain do this

it's what we call muscle atoni now I was

telling you that we measure your

electrical brain activity and we measure

your eye movement activity but we also

measure your muscle activity why do we

do that well as you're going into

non-rem sleep that muscle tone decreases

but there's still some muscle tone there

but as you go into REM sleep in fact

just a few seconds before you enter REM

sleep I already know you're going into

RAM sleep because bang you you become

completely absent of muscle toone

and if I were to pick you and I mean I'm

I'm probably not going to be able to

pick you up out of your bed um based on

certain images I've seen on social media

um I'm going to if I lift you up you'd

just be like a rag doll you'd have no

muscle tone whatsoever it's almost like

those toys where it's like a donkey that

sits up and it's got a button underneath

and you press the button whoosh and it

just falls down I used to have those as

a kid too like the simple things that

you and I had as children that would

fate still own a couple of these but

they but yeah I need to get a donkey one

um in any event um I know what you're

referring to so this this muscle and as

we call muscle Aton and I think in sort

of medicine usually with an a before it

means the absence of something so sort

of if you're if you have arhythmia

absence of normal arhythmia aasia yeah

sort of or um and here it's aonia

absence of the tone in your

muscles why would the brain do this well

the brain paralyzes your body so your

mind can dream safely you would imagine

how quickly you could be popped out of

the G pool if just like you described

you thought I can fly so you get up out

of your bed and you go to the window and

you launch probably not going to end

well depending on what floor you're on

so this absence of muscle tone this

physical incarceration that we have is

one of the things by the the way that

defines REM sleep from when you are

awake because if all I was doing in my

sleep lab was recording your electrical

brain activity and I was in the other

room and I was just looking at your your

brain waves as you go into REM sleep I

would not be able to tell are you in REM

sleep or are you awake why because the

electrical brain activity is so similar

when you are in REM sleep relative to

when you're awake and what that tells us

is that REM sleep is an incred

incredibly active cerebral condition

your brain is just firing away in fact

some parts of your brain can be up to

30% more active when you're in REM sleep

than when you're awake stunning

particularly emotional brain centers so

it's a it's a stunning state of of

paradox and that's the reason that we

sometimes call it paradoxical sleep your

body is completely

immobilized

utterly inactive but your brain is

fervent with its activity by the way

people should not worry when I say that

you are your your muscles are shut down

and what happens is that as just before

you go into REM sleep there's a bursting

activity that will go up into your brain

to light up your cortex but there's

another signal from the brain stem

that's sent down all the way down the

spinal cord to the Alpha motor neurons

in the spinal cord that will essentially

create this inhibition it's only your

voluntary sceletal muscles meaning that

your involuntary muscles things for

example such as your respiration that

helps you breathe in your heart that's

the reason that we you know survive and

live another day after sleep so don't

worry about that too much with two

exceptions though there are two sets of

voluntary

muscles for reasons that we still don't

know either that are spurred from the

paralysis of REM sleep one of them is

the extraocular muscles and that's the

reason that when you go into REM sleep

you can have these darting horizontal

movements back and forth those should

also have been paralyzed but they're not

and then oddly there is a a muscle in

the middle inner ear muscle that does

not undergo the paralysis and it will

also twitch too just like your eyes but

I'm getting into the weed so that's

what's happening in these different

physiological States and to your

question when you don't have any muscle

tone whatsoever maybe that is imp part

the reason why a you can start to have

these dreams of absent gravitational

pull meaning you can start to fly it may

also be the reason by the way that

coming back to propri reception you can

sometimes have that feeling of some

people will describe my teeth are always

falling out I always feel as though it's

a very common thing to to or you feel

the absence of clothing on your body and

you say I walked out and I was going to

this meeting and I realized I didn't

have any pants on and and you forget

that proception is also about knowing

that your clothes are on you and sensing

those clothes you and I can now direct

our attention and sense those clothes on

us is it also the case that um when we

talk about sleep we talk about falling

asleep that the sense that one is

falling back into their head I um is

related to the progressive loss of

propri reception in the early stages of

sleep or is it just semantics no I often

think that that may have being where it

that that notion comes from

we why would we not say that I am

sometimes people say I'm drifting off

into sleep but or I'm about to enter

sleep and we say I'm I'm falling asleep

now some of that may be that I'm falling

into a sort of a deeper and deeper state

of a brain wave activity pattern maybe

but I actually think you're right now we

don't know ultimately the origin of it

but I believe it's imp pop because

people have this sense of falling hence

falling asleep along those lines um I've

found that if I sleep horizontally on a

bed or sofa um the sleep is Far and Away

different than if I'm fall asleep

upright in a chair or partially upright

in a recliner yeah um

for instance on an airplane now there

are a bunch of other things happening on

airplanes Bright Lights noises Etc um so

it's not a a good experiment to compare

those two situations airplane recliner

versus uh in bed at night um too many

variables temperature especially but um

is there any evidence that one's bodily

position during sleep or the uh

orientation of the feet relative to the

head you know the angle elevated upward

or downward has any impact on the uh

pattern of of different sleep stages or

uh quality or uh any other aspects of

sleep there is a reason for it and we'll

probably come on to this at some point

when we speak about different methods

for Sleep optimization or the new wave

of of fascinating sleep enhancement

tools has to do with temperature we

think that for you to be able to fall

asleep and stay asleep you have to drop

your brain and body temperature by just

a little less than about 1 degre Celsius

or probably two two and a half degrees

Fahrenheit and that's the reason by the

way that you will always find it easier

to fall asleep in a room that's too cold

than too hot because the room that's too

cold is at least taking you in the right

temperature direction for good sleep

whereas the room that's too hot the

opposite it turns out that the body's

ability to dissipate heat what we call

Thermo regulation here and Thermo

regulation in One Direction which is

which is the reduction in core body

temperature is superior when you are

lying down versus when you are inclined

versus when you are standing up really

and in part it has to do with the

distribution of blood throughout certain

parts of the brain in the distal versus

proximal regions meaning sort of the

regions that are Clos to the core of

your body versus the regions that are

further away but your body's ability if

we largely take most item items of

clothes off you and then we measure the

the core body temperature and the way

that we do this um it's a delightful

technique it's called a rectal probe and

it's neither Pleasant necessarily for

the installation of the the the the

experiment of doing it and it's

certainly not necessarily for the

participant but putting that aside for a

second they we can measure your core

body temperature and we can measure

using temperature sensors all over your

body exactly what's going on with the

blood flow and we can measure how the

brain is starting to dis ipate the heat

because one of the principal ways that

we dissipate heat from our body is by

moving blood around the body when we

bring blood into the core of our body

we're trapping it in the core and our

core body temperature increases when we

push that blood out to the surface it

goes to these thin sort of capillaries

and vessels on the surface of your skin

and you start to dissipate that heat and

you dissipate it more quickly so your

core body temperature drops and the

body's sort of vasoactive capacity for

Distributing that blood and then

releasing that trapped heat from the

core of the body is superior when you

are lying down and therefore your body

temperature can drop more quickly which

is one of the many reasons why it's not

as easy to fall asleep when you're sort

of at a 45° angle and why the quality of

your sleep won't be as good now there

are other reasons to just as you

mentioned but coming back to

position I would say that there are

maybe there's perhaps at least two

pieces of evidence that would recommend

positional differences or positional

changes the the first is very obvious if

you are someone who is snoring and you

have certainly if you have untreated

sleep apnea which is um where you're

sort of not just snoring but you'll have

an absence of breath that's what the

word apnea means here's another one with

an a in front of it pinea sort of you

know you've heard of pneumonia and it

this is about breath and apnea is about

an absence of that breath and with sleep

apnea not only do you start to have an

airway collapsing partially and that's

where you get that flutter and that's

the sound of the flutter that we're

having but then at some point you just

hear silence and at that point the

person's stop breathing entirely absence

of breath that is much more likely to

happen if you are sleeping on your back

because when you're sleeping on your

back your Airway is giving way to

gravity which is wanting to pull the

airway down and close it and shut it off

so one of the suggestions for people who

have snoring or sleep apne is trying as

best you can to train yourself out of

sleeping on your back now there's lots

of gadgets out there that can sort of

help and ways can do that the old school

way that we used to do it um sleep apne

is more common in men than it is in

women but women still have it but if you

had a male you would bring them into the

the clinic and you would say could you

and it's often males who perhaps are

carrying excessive body weight and so

they're of larger Mass size You' say can

you also bring a t-shirt in uh of your

wife and it has to be a t-shirt that is

that has a pocket on the front and then

we would ask them to wear the T-shirt

back to front so it's a very tight

fitting t-shirt it's back to front and

then you took a tennis ball or a hockey

ball in the back pocket and as you're

lying there in bed and you turn over

onto your back you get this painful

signal of the tennis ball pushing you in

the back and it gradually I know who

came up with this is this Matt was this

um Matt Walker's idea this is not me I

am not it's clever yeah I should now be

on social media I should be changed to

sort of like sleep torturer rather than

sleep Diplomat um so that's one

recommendation try to stay clear if

you're asking me are there certain

positions we should stay away from in

that circumstance yes it would be the

other comes back to something I

mentioned during deep sleep when this

cleansing system starts to kick into

gear in your brain and wash away these

toxins from the

day what we've

found a little bit of evidence and we

and the Royal we because I um like you

my lab doesn't do um animal research we

only do human research but some animal

researchers had discovered that when

animals will sleep with their head on

the side the the cleansing capacity of

the brain is superior than when the

animal is sleeping on its back or

sleeping on its front and in fact if you

look and you would love this project if

you go on to Google and you just search

for sleeping animals look at the head

position and I will guarantee you that

many of them if they're naturalistic are

animals with their head turned to the

side now the cute ones the funny ones

are when a you know a kitten is SPL out

on its back and its head is back that's

how someone with sleep apne would sort

of sleep on their back and but that's

very rare we almost never see that so

it's very interesting and what they

found was that when those heads were in

those sort of side positions the

cleansing mechanism of the brain was a

little bit better it wasn't night or day

it's not as though oh my goodness I'm a

front sleeper and you know I'm not

getting any brain cleansing or I'm a

back sleeper and not I'm not saying that

there's no need to take it to the

extreme but I I don't think there's any

good evidence yet in humans that firstly

that's the case and nor is the strong

enough evidence to make any

recommendations but I just bring it up

because it's in the data and it's

starting to emerge that if you were to

ask me about sleeping position and are

there any recommendations those are the

two pieces of descriptive advice I would

give you they are not prescriptive

pieces of advice you mentioned the

relationship between temperature and

sleep and we're going to get into that

uh in some degree of detail a little bit

later because it's so critical but um

prior to starting to record this episode

we were talking a little bit about

yawning um and you told me something

really truly fascinating about yawning

which

was so there are at least four competing

theories of yawning that we have and I

think there is probably a emerging clear

winner um the first theory was that it

was just tiredness that yawning is

simply a sign of you being tired and it

turns out that that's not true because

many people can yawn when they're

bored and they are not tired and they've

been very well rested so that doesn't

seem to be true the next one was one

that that seems to be very logical which

is it's about trying to rebalance your

blood gases and specifically oxygen and

carbon dioxide and you would think that

perhaps when you yawn with that sort of

when you and you inhale a huge volume of

oxygen what you're trying to do is pump

back up the oxygen in your bloodstream

or when you sort

of and the exhale maybe it's about

exhaling more carbon dioxide not unlike

the physiological size that occur during

sleep of a double inhale with a long

exhale correct or that one can

voluntarily generate for anxiety

Management in wakeful St exactly Y and

so that was a a theory that maybe you're

trying to balance these these blood

gases and there was some very clever

experiments where they took it

individuals and they artificially

increased their oxygen uh levels but

more specifically they increased their

carbon dioxide levels by directionally

they tried to manipulate it and they

asked did those individuals start to

yawn more because the idea would be if

your blood oxygen is coming down and

your carbon dioxide is starting to rise

if this theory is correct you should

start yawning with greater frequency and

there was no difference whatsoever

that's probably also the reason that you

don't see people yawning on a treadmill

or when they're going into more of an

oxygen debt and higher levels of carbon

dioxide so that theory was knocked out

the third theory was one of

contagion and it's fascinating yawning

like several other things has a

contagious element to it so as the

audience unexpectedly they didn't know

what you were going to say and before

you said it you said you told us

something interesting

about and you did I guarantee you that

there will be people listening right now

who said oh I just yawned in response to

Andrew hubman yawning it is very

contagious in part it's the mirror

neuron system and you've obviously

understand this in depth your brain has

this capacity to mirror the action

states of other individuals so a good

example would be let's say I'm walking

out the door now I'm closing the door

with my hand and all of a sudden I'm

going to get my hand trapped and you on

the other side of the room you are

seeing my hand and as soon as I trap my

hand and I Yelp out in pain you almost

hold your own hand oh because why why

why are you doing that it's not just

because you know you're trying to be you

know compassionate no you have

experienced some degree of what I've

just experienced how does it do that

because your brain has a system inside

of it that mirrors my action States and

it's called a mirror system and you can

imagine why it's very good to understand

the action and emotional states of

others for pro-social capacities and all

of that good stuff and one of the things

that can also happen with this mirror

neuron system is that it mimics yawning

so when you yawn my likelihood of

yawning increases too because my mirror

neuron system is matching your Y and

what's interesting is that we know other

species also have a mirror neuron system

and that means that when you ywn there

is a statistically higher chance that

your dog will yawn and it's cross

species so when your dog

yawns there's a higher probability that

you will yawn and we've got this St and

it's it's very clear one of the other

interesting theories though is that when

um species that are Cooperative species

for example a pride of life

Lions when one of those Lions yawns

firstly many of the other Lions will

yawn in a contagious fashion but then

consequently there is a collection of

actions that happen after that

contagious yawn and so some people have

suggested that the yawning is a way to

enact Cooperative group Behavior that's

another theory the final Theory number

four which I think has the best evidence

for is not the gaseous exchange

balancing of carbon dioxide and oxygen

but when you inhale oxygen from the

outside it's usually cooler than your

core body and brain

temperature and when we inhale there is

a modest drop in brain temperature and

when the brain temperature starts to

rise that's when we see yawning

frequency beginning to increase so next

time you see someone yawn don't think oh

they're bored or they didn't get enough

sleep go over to them hug them and say I

know your brain is getting warm it's

okay and then at that point the

friendship will be terminated because no

one should be hooking each other and

saying your brain is warm I'm so sorry

but anyway that aside um I'm sorry we I

took us down that that um tributary of

my polluted stream of Consciousness but

that's yawning explained those are the

four theories and we don't have a

definitive answer but I think the best

one right now that will continue is that

it's about brain cooling that theory

makes a lot of sense um people tend to

yawn when they get tired as you

mentioned people can yawn for other

reasons as

well if I'm yawning because I'm tired

and yawning is to cool off my brain

that's too warm is that an attempt to

put my brain to sleep because we need to

cool the brain in order for it to go to

sleep or something else going on there

also and this um sort of merges with the

previous question about body position

I've lectured in the university for you

know well over a decade as I know you

have as well and occasionally every once

in a while there's one student I'm just

kidding there are several students

especially if it's an afternoon

class or a very early morning class that

is falling asleep in their chair and

then their head they kind of jolt awake

and we all know that keeping the room a

little bit cooler sometimes helps to

keep people awake

um as opposed to a warm afternoon

classroom but in some ways what we're

talking about here um violates what you

were talking about earlier that it's

easier to fall asleep in a cool

environment as opposed to a warm

environment uh the brain needs to cool

in order to fall asleep but then when we

yawn it's in response to the brain being

too warm and so um and so I'm I'm having

a little bit Circle for me yeah help me

understand square square that Circle I

like it yeah please square that Circle

for me Matt um it turns out that for you

to drop your core body temperature the

opposite has to happen which is that you

have to warm up to cool down to fall

asleep and I mean warm up in a very

specific way you have to have the outer

surface of your brain warm up you have

to get blood to the surface of your skin

and that surface it almost acts like a

snake charmer that it Dr draws the warm

blood from the core and it pushes it to

the surface and you radiate the heat out

and as you radiate the heat out said

your core body temperature plummets so

why would people be falling asleep sort

of you know in an afternoon meeting when

it starts to get a little warm well in

part it's because the warmth of the room

is starting to make the sort of face a

little bit more Rosy it's drawing the

blood out to the surface so what's

happening the core of your brain and

your body temperature are starting to

drop and at that point that's why you're

going to start to feel a little bit more

sleepy that's reason one the second that

you described is that afternoon you know

you're in meetings around a table and

you start to get as you said those

wonderful head nuts and people listening

you you all know that where the of head

goes down and snaps back up it's not

that people are listening to good music

and sort of doing this head bobbing it's

that they falling prey to what we know

is a genetically hardwired

pre-programmed drop in your afternoon

alertness it's called the postprandial

dip in alertness and that infers that

it's after some kind of a a meal it

turns out it's not really related to a

meal people say well I had a heavy lunch

I had sort of pastor at lunch and I

always feel sleepy afterwards maybe in

part but if I remove I prevent you from

having lunch and we've done these

studies too your brain still shows this

very reliable drop and alertness

somewhere between quite wide but

somewhere between about 1: to 4:00 p.m.

in the afternoon yeah for me it's always

between 2: and 300 p.m. which uh is a

time I'm resisting looking at my watch

right now just to see yeah we might be

in that in that uh phase of the day uh I

can always feel it and um if I close my

eyes for 10 20 minutes um it I usually

can fall asleep pretty quickly yeah for

a nap I know we'll talk about naps later

um but if I don't and I ride it out I

then you know usually by about 3 3:30

I'm fine get that rise back up don't you

and it sort of swings back up and so

that's in part the reason though

explaining the yawning and that that

warm feeling of I'm in the the meeting

room the boardroom meeting and the the

the blinds are open the sun is coming

through I've got the sun on my back I'm

starting to get very warm but I'm

starting to get really really sleepy

it's

the it's the collusion of two things

it's that you're going into this higher

frequency sleep Zone in the afternoon

this postprandial drop in your brain

alertness and we can measure it it's

very reliable you can see this dip in

your brain electrical activity and

you're getting warm at the surface which

brings blood to the surface releases

that heat from the core it drops and boy

do you want to fall asleep I want to

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tracker.com

huberman I took us on a bit of a journey

into some um I don't want to call them

sidebars but some uh specific features

around sleep and falling asleep

Etc let's get back to the different

stages of sleep and frame that under the

question of what is great sleep what is

mediocre sleep I think we all know what

bad sleep is it's when you can't get

sleep but I think there's a whole

different category of bad sleep that

you're going to tell us about which is

sleep that we think is good but is

actually not as good as we we think it

is I'm always the barer of Doom and

Gloom no well and but also but also the

um the deliver of of powerful tools to

improve one's one's sleep and thereby

wakeful state so along those lines you

know what is sleep for truly and what

happens when we don't sleep well is

perhaps more intuitive to most people

you know oh I feel cranky or I can't

remember things or I just kind of you

know um stress seems to feel a little

more intense the same amount of stress

feels more intense um and what is great

sleep you know and and and this is I

think all under the umbrella of of you

know why do we sleep I mean why do we

spend a good third to you know or more

of our life in in this incredible state

of mind and body that we call sleep and

it really is quite a

stunning state of

idiocy when when you consider it because

when you're asleep you're not finding a

mate you're not reproducing you're not

foraging for food you're not caring for

your young and worse still you are

vulnerable to

predation on any one of those grounds

but especially all of them as a

collective sleep should have been

strongly selected against in the course

of evolution and in fact one of the

founding fathers of sleep research Alan

re shaen once said that if sleep doesn't

serve an absolutely vital function it is

the biggest mistake The evolutionary

process has ever made and now what we've

learned

through you know almost 10,000 plus

research studies over the past certainly

70 80 years now is that nature did not

make a spectacular blunder in creating

this thing called sleep so maybe I can

firstly address what is what is sleep

doing and what happens if we're not

getting sufficient sleep and then the

other question is what is what is good

sleep in terms of what sleep is doing

and why he was right in saying that

mother nature didn't make a a blunder

and it hasn't by the way because if you

go back every species that we have

carefully studied to date seems to sleep

and what that tells us even you know

very old evolutionary old ancient um

earthworms seem to sleep they will have

a period of what we call theargus which

is they seem to be

inactive so what I I bring that point up

because it means that sleep appears to

have evolved with life itself on this

planet and then it has fought its way

through heroically every step along the

evolutionary path and that by itself

must tell us that whatever sleep is

doing it must be

non-negotiable life support

necessary in what ways is it life

support necessary well we now know many

of those first when you're not getting

sufficient sleep I can speak about your

hormonal

systems let's say I take a group of

really healthy young men and I limit

them to four or five hours of sleep for

five nights they will have a level of

testosterone which is similar to someone

who is probably 10 years older than them

so a lack of sleep will agid you within

5 days by a decade we also see

equivalent imp uh imper in female

reproductive Health caused by a lack of

sleep impermanence in estrogen in

follicle stimulating hormone and also in

lutenizing hormone what what about the

uh effects of a single night's poor

sleep on on hormones um and not to get

too down in the details here but uh is

it necessary to have four or five nights

of minimal sleep in a row before you

start to see these effects or let's say

somebody's getting good sleep for three

nights or four nights of the week but

then the other three are kind of

challenging for whatever reason does one

see a graded effect a kind of

intermediate reduction in sex steroid

hormones like testosterone estrogen

follicle stimulation there is some

degree of a dose response curve but we

haven't mapped it out with high so the

way I would want to do it as a sleep

scientist would say okay I'm going to do

this for one night and I'm going to thin

slice you to seven hours 6 hours 5 hours

and then I'm going to do it for two

nights and you're going to again be in

the 6 hours 7 hours 4 hours and I would

like to build up this High Fidelity map

and understand that we don't have that

but certainly what we know is that a

night of total deprivation will markedly

imper those hormones and we know that

after about you know a working week of

short sleep you see those imp perance

too um but let me come back to one night

so that's the hormonal system as an

example and we've already spoken or I'll

come back to it um right now the

metabolic system and another hormone um

insulin what we found is that if I take

you again and I limit your and you're

perfectly normal healthy you don't have

any signs of type 2 diabetes and I limit

you to let's say 5 hours of sleep for

four nights and then I measure your

ability to dispose of blood sugar and um

your level of blood sugar impairment is

so disrupted that at that point your

doctor would classifier as being

pre-diabetic so I could take an

individual and within five nights of

short sleep I can move them towards a

path that's getting very close to type 2

diabetes and as I said we've UND and we

Royal we here um whenever I say we by

the way it usually means that um well

whenever I say I did something I mean at

my Center we did something and when I

say we did something I mean that they

did

something that's a a fair Shand for uh

for attribution um and so so there there

have been studies that have really

decomposed exactly how that impermanent

in blood sugar happens and we mentioned

that earlier in this episode I can also

then move on to for example your um your

immune system this is a very good

demonstration firstly there's a great

study done by Michael ow and his

colleagues at UCLA and he took

individuals healthy individuals and he

limited them to just four hours of sleep

for one single

night and he measured levels of critical

anti-cancer fighting immune cells called

natural killer cells and what he found

is that after that one night of Just 4

hours of sleep there was a 70% reduction

in natural killer cell activity that is

a striking state of immune deficiency

and just to give people a you know a

reference point these natural killer

cells were think of them almost like the

secret service agent of your immune

system these natural killer cells they

are very good at identifying dangerous

unwanted elements in your body like

cancer and going after them and

destroying them so you wish for a very

verile set of these immune assassins in

your body at all times and if you're not

getting sufficient sleep that may not

necessarily be the case we also know

that if you are not getting sufficient

sleep in the week before you get your

flu shot and this is just another

example of how sleep is critical for

your immune system if you're not getting

that sleep in the week before you get

your flu shot you produce less than 50%

of the normal antibody response

therefore rendering that flu shot

largely ineffective in terms of

vaccinating you we also know that if

you're not getting sufficient sleep on

average let's say that you're getting

less than 6 hours of sleep or less on

average you're almost three times more

likely to develop the common cold common

flu and I know that you at the time of

us recording this um you've released

some fantastic content about the the flu

and and the Rhino virus in particular so

that's a good demonstration of your

immune system we also know that it's not

just that it's also your cardiovascular

system that suffers when you're not

getting sufficient sleep and here again

the data I think is very strong

cardiovascular disease RIT large

including stroke and and heart attack

and there is one study that I think

illustrates this and and granted now in

terms of the replication the effect

sizes may not be as big but the study

was

interesting they didn't do something

radical like depriving you of sleep for

an entire night nor did they just limit

you to 5 hours of sleep for you know

four nights there is a global experiment

sleep experiment that has performed on

about

1.65 billion people across 70 countries

twice a year and it's called daylight

savings time now in the spring when we

lose an hour of sleep what they observed

in that paper was a 24% relative

increase in heart attack risk the

following day yet in the autumn in the

fall when you gain an hour of sleep

there was a 21% reduction amazing in

heart so it's bidirectional and by the

way and I I said that that paper there

are you can there are some aspects that

you can sort of discuss but it has been

replicated we see increased rates of

hospitalization after that 1 hour of

lost sleep in the spring there are

higher rates of car accidents on the

road after 1 hour of lost sleep we also

see higher rates of suicide after 1 hour

of lost sleep during the spring time

change we even see this is great data

they they looked at um the sentencing of

federal judges in the United States and

because it's the federal system the

government system all of those things

are cataloged and well documented you

have a huge database and they went back

and what they found is that in the

spring when we all lose that 1 hour of

sleep

opportunity those judges doled out

harsher Federal sentencing in the day

after they had lost one hour of sleep

because their emotional and mood states

were imper and we'll speak about this in

a later episode too so if you are up for

sentencing or please try to avoid that

spring time change as best you can go

for the go for the fall date if if it's

possible um so that's that's your

cardiovascular system I could also tell

you that it goes all the way down into

the cellular and molecular state of your

body and this I'm trying to do this to

impress the fundamental importance of

sleep there was a wonderful study done

by my colleagues at the University of

Sur back in the UK by led by duk Yandy

and what they demonstrated was that if

you take healthy individuals

and everyone is going to act as their

own control and you limit them to um 6

hours of sleep for one week versus

allowing them to sleep at least 8 and 1

half hours or more time in bed and then

what they did was they measured the

change in their gene activity

profile relative to when those same

individuals as I said were getting a

full 8 hour plus opportunity in bed

versus the 6 hours of limited sleep and

they found two interesting things first

a sizable and significant

711 genes were distorted in their

activity caused by a lack of sleep by

the way that's relevant we know that

almost one out of every three maybe even

one out of every two if you look at the

data people that pass you on the street

is trying to survive on six hours of

sleep or less during the week so it's a

relevant ecological

manipulation the second result was that

about half of those genes were increased

in their activity the other half would

decreased now those genes that were imp

purred by way of one week of short sleep

were genes associated with the immune

system so once again you can see this

immune deficiency but now playing out at

a genetic level those genes that were

increased or what we call overexpressed

were genes that were associated with the

promotion of tumors genes that were

associated with long-term chronic

inflammation within the body and genes

that were associated with cellular

stress and as a consequence

cardiovascular

disease and to me that study impressed

the fact that there is no aspect of your

Wellness that seems to be able to

retreat at the sign of sleep deprivation

and get away unscathed it's almost like

a broken water pipe in your home that

sleep will leak down into every knck and

cranny of your physiology and it will

even tamper with the very DNA nucleic

alphabet that spells out your daily

Health

narrative so I I paint this this picture

which seems dire and it I think someone

once said to me look your your Ted Talk

which I think it was called Sleep uh

sleep is your superpower they said that

talk should have actually been sleep or

else dot dot dot which was a completely

fair thing because I think you know very

early on as a public figure for sleeper

um I did a terrible job I was very

dictator I was very disagree um well I

was I think I think I was very

absolutist and I've I've learned my

lesson I'm I disagree and and um and I'm

going to interrupt intentionally uh not

to to Puff you up just because but I I

think that it's fair to say I know it's

fair to say that the cautionary notes

that you spoke about in those early TED

talks and in your book why we sleep um

while they may have stimulated some

anxiety for some people uh they

absolutely

had and have a net positive effect in

the sense that they cued people to the

importance of this thing called sleep

because prior to you doing that or those

things it was the case that it was the

I'll sleep when I'm dead mentality um

and as somebody who's pulled many

allnighters in his career many many um

although not these days any longer thank

goodness um I can tell you that that

information was transformative for for

my behavior and also for people in the

Arenas of military Sports children

adults I I it is fair to say that we

have better parents better kids better

citizens of every country as a

consequence so I I uh won't allow you

one of the few things I'll I you will

have a hard line on I won't allow you to

U malign your contribution um and the

good news is this series is also going

to include a lot of discussion about

things that one can do anyone can do to

improve their sleep so yeah and so

enough with that for saying that I will

I will stop trying to reject that um but

I would also folks put in the comments

on YouTube whether or not you agree with

me or you agree with Matt and then um

you know uh and thanks for agreeing with

me um I would say though that please

don't start as you mentioned there

you're getting anxious if you're not

finding it easy to fall asleep that

listen

to me is firstly probably not going to

make matters any better but don't think

even if you're in the general public

that look I had one bad night of sleep

does it mean I'm now going to develop

Alzheimer's disease absolutely not

there's we're not suggesting that we're

talking about a model in which you know

week after week month after month yes

I've demonstrated that you know after

just one night of something of short

sleep you can see measurable impairments

and we can and I can't you know I can't

be untruthful about the scientific data

but it's not as catastrophic as one may

think and as you said in this series we

will also speak and focus a great deal

about what can you do to start to try to

optimize your sleep so thank you for

that opportunity absolutely so lots of

things not good for us happen when we

don't sleep enough on a consistent basis

yes one poor night's sleep let's face it

I mean our species would cease to exist

if if that were the case because all

these parents that have stayed up where

you have a you know an emergency or that

the neighbor's dog is barking or you you

go to an airb B where it's too warm and

and you can't sleep I mean um but

clearly bad things start to happen when

we are chronically sleep

deprived we hear less often about the

great things that happen when we get

great sleep um perhaps we can talk about

a few of those I mean obviously um many

of them are going to be the inverse of

what you just described but uh for

instance learning neuroplasticity the

nervous system's ability to change in

response to experience uh sleep

deprivation impairs learning yes yeah um

and a great night's sleep makes it a lot

easier to learn right so what are the

data in terms of the relationship

between sleep and learning again

something we're going to go into in

quite a bit more detail but can you give

us a um uh can you can you throw us a

bone about some of the can you

incentivize us for getting good sleep

not just through fear but we heard the

sticks um you know throw us a carrot

yeah so there are so many wonderful

carrots so when you are sleeping your

brain's capacity and its Learning

Centers are so much more ready to absorb

information so think about these memory

centers in the brain almost like a dry

sponge if you've been sleeping well and

they are so excited to soak up new

information and retain that information

so firstly sleep before learning is

going to help you acquire and imprint

new memories very effectively and we've

demonstrated that we I'll tell you about

the studies in in a later episode we

also know though sleep after learning

does something delicious it will take

those freshly minted memories and it

will consolidate them into the brain

meaning that it will start to fixate

them almost like sort of setting them in

concrete into the brain and so you are

far less likely to lose those memories

which is to say you are far less likely

to forget if you've been sleeping after

you've

learned it's not just that though sleep

does more than simply strengthen those

individual memories sleep will start to

Crosslink and connect those memories

together and as a Consequence the next

day you will wake up and those that

memory back catalog has now been updated

with all of the recent information and

it's integrated and it's Associated so

you are now able to come up with new

Creative

Solutions to issues or problems that

you've been facing because you've

updated what we call the associative

networks in your

brain and this is the reason that people

will describe having had these insights

by way of sleep and these problem

solving capacities and really that's

what to

me a good student is not simply a

student who can learn all of the

individual wrote facts and then just

regurgitate them an

individual memory is not as sitting as

an isolate island is not particularly

useful that's why your laptop isn't well

as long as it's not connected to the

internet and and uh open AI it's not

particularly

intelligent I mean it has a storage

capacity that is almost more perfect

than your brain it doesn't make some of

the the memory sort of mistakes that we

do the reason it's not as intelligent as

we are in part is because it has not

integrated the information it doesn't

link all of the wouldn't it be wonderful

if you woke up one day and you'd

installed a program on your computer and

your computer just understood how all of

the files were interrelated and

connected and it was saying okay you you

know you've double clicked on this file

well now I'm going to tell you that

there is this related information you

should pull this in here and it would

enhance this paragraph that you're

working on or it would improve this

experimental idea that you're coming it

doesn't do that but your brain does that

how does it do that in part it's because

sleep is building these associative

networks so it's not it's not simply the

student who learns the rote facts it's

the student who learns the facts and

then understands what they

mean sleep is not just about learning

and it's not just about knowledge it's

about wisdom which is knowing what it

all means when you fit it together and

that's one of the other roles of sleep

so those are some of the beneficial

things the sort of the the carrots that

can come by way of for your learning and

memory there are so many other carrots

though we described for your immune

system how there is this restoration

that happens during deep sleep and it

primes that but there are other benefits

too one of the things that we've

discovered and we hopefully we'll get to

discuss this in more detail is that

sleep

provides almost a rebooting of your

emotional and your mood

States and as a consequence you wake up

the next day and you are dressed with a

very different set of emotional

clothing and sleep when you're getting

it almost it's like a set of emotional

windscream wipers that it's just cleared

those things off and you wake up it's

the reason that people will tell you you

know

you if something is troubling you don't

worry just come back tomorrow just give

it a night of sleep and you'll probably

feel better tomorrow that feeling better

notion is sleep acting as this emotional

bomb that just soothes that those Jagged

edges that we've you know be sort of

almost like a CD getting scratched if

anyone out there knows all a CD is these

days but you know these scratches that

we get emotional wounds sleep is

starting to heal those as well so those

are benefits I could also mention some

other aspects of your weight control and

your weight gain and this is a huge huge

effect size Sleep moves the needle on

almost every aspect of brain and body

health I think it's very clear at this

stage that there is no single tissue or

major physiological system in your body

and no operation of your mind that isn't

wonderfully enhanced by sleep when you

get it or demonstrably imper when you

don't get enough but when it comes to

appetite and regulation of weight gain

this is immense firstly what we know is

that when you're getting sufficient

sleep you can create a a nice

um concentration ratio of two appetite

regulating hormones called leptin and

grin and let me go sort of in the

reverse to probably give you a better

example let me say I deprive you of

sleep and what we see is that these two

hormones that and I joke you know that

sometimes sound like um leptin and grin

sound like Hobbits from Lord of the

Rings but they're not they're real

hormones and leptin essentially is the

signal that tells your brain okay your

you're satiated by your food you're full

and you don't want to eat more so hunger

and appetite decrease grin does the

opposite when grin increases now it's

the signal of hunger and you get

increasingly unsatisfied despite eating

a f full meal if you've got still high

levels of grin you don't feel satisfied

with that meal and many people listening

may start to say I have this feeling

where I'm just eating and I just don't

feel satisfied on some days and those

days

I suspect can be days when you are not

sleeping well and I think everyone has

had this feeling of saying I just didn't

sleep well last night and I I just get

ravenous and my I just unleash this

Unholy hunger and an appetite that's in

part because these two hormones so what

happens is that when we're not getting

sufficient sleep leptin the signal that

says you're satisfied with food stop

eating that is imper by way of a lack of

sleep if that wasn't bad enough the

hormone grin that says no you're not

satisfied with your food eat more that's

the signal of hunger that increases so

it's almost like double jeopardy you're

getting punished twice for the same

crime of not sleeping once by way of a

drop in leptin stop eating and once by

way of growling foot to the floor

acceleration I want to start eating

that's in part why you're going to your

waistline can start to expand when

you're not getting sufficient sleep but

when you do it's a it's a fantastic way

of controlling I guarantee you if you

start to implement better sleep your

ability to regulate your basil levels of

appetite and hunger will

decline but it's not just that you want

to eat less or you at least want to eat

an appropriate amount for your body mass

it's also what you want to eat and what

we've discovered is that when you are

again not getting sufficient sleep you

start to eat more more yes you do but

you eat more of specific things you

crave things like these heavy hitting

sort of stodgy carbohydrates like bread

and pasta and potatoes and pizza and

also you crave simple

sugars and so those Foods we know in

excess can be what we call obesogenic

Foods they are foods that can lead you

to a more rapid amount of weight gain

whereas when you are getting sufficient

sleep now you're reaching at the food

bar for you're saying what I think the

the salad and those healthy nuts and the

fruits and those things look quite

appetizing today versus when you are

underslept all you want to do is go

after the junk food and because you kind

of got these Munchies what's interesting

is that a recent discovery came back to

that notion of the munchies when I say I

got the munchies people sometimes think

of a drug reference they'll say well

been smoking weed I always get the

munchies why is that because when you

when you are bringing in cannabis into

the body and these canabo these what we

call exogenous canabo they will increase

your appetite they will stimulate your

appetite cannabinoids are appetite

stimulating components but we all have

our own version of cannaboids that we

produce inside of our body that you've

spoken about before called endoc canabo

when you are underslept the brain

releases more endoc canabo and that's in

part why you get this strong impulse for

and thus IO when you start sleeping

better you moderate all of these

hormones and these chemicals and your

appetite is controlled when you eat you

feel satisfied with your food you're not

craving more when you make your food

choices you're making better food

choices we did a study with brain

Imaging where we underslept individuals

and we had them see food items inside of

a brain scanner and they had to rate you

know how much do I desire and how much

do I want these items and those items

range from very healthy items all the

way to unhealthy items things like ice

cream and sort of pizza and all of that

good stuff and sweets um Candy as you

would say over here and we looked at

their ratings and by the way we to make

this a more ecological because you could

say Well they're going to know what's

the healthy choice so they're probably

just is going to be you know politically

correct and say oh I desire the healthy

food because the way that we tried to

get around that was we said anything

that you said was desirable when you

come outside the scanner we've actually

got all of these foods and you're going

to have to eat them um so they were

making more real realistics and each

person went through the experiment twice

one night after full nights of sleep one

night with significantly less sleep and

sure enough inside of the scanner they

were rating unhealthier Foods as more

desirable so your preference was going

in that unhealthy Direction but what was

interesting was what was going on in the

brain we saw that the frontal lobe

regions these sort of areas that sit

above our eyes that almost act like the

COO of the brain and they help regulate

our deep emotional centers those regions

of the brain had gone offline by way of

a lack of sleep and these emotional

centers that are usually associated with

more honic reward and they're also

excessively more active in people with

obesity who have what we call honic

eating patterns those regions were

ramped up by way of a lack of sleep so

it's not just that there are chemical

changes in your body that conspire to

have you eat more there are also changes

in your brain that prevent you from

making the healthy food choices but when

you're getting sufficient sleep in the

control condition when they were getting

that sleep their brain was beautifully

regulating the optimal food choices so

that that's just another example of a

car carrot no pun intended now um that

when you're getting sleep if one of the

ways you want to manage

your your body composition and manage

your appetite is by way of getting

sufficient sleep it's actually a very

powerful tool that we probably underrate

and then this other aspect I would say

is emotional and mental Wellness

everyone knows that your emotional and

mood States will take a nose dive like a

Dart into the ground when you're not

getting sufficient sleep it's that idea

of I just snapped dot dot dot and those

are the words that usually you know are

uttered by people who are not usually

sleeping very well but when you're

getting good sleep it's so much easier

to regulate and manage those emotions

and Michael Grand know great sleep

research he did an interesting study and

it was one of those studies many studies

I read from my colleagues that my

initial reaction to the study was

jealousy because it was such a good

study and I was jealous that I didn't

think of the idea and now gradually with

my senior age I've disabused myself of

that ego and very quickly I then think

this is the best faor and I can't wait

to tweet it out but he did a great study

and it was only quite recently he asked

what are the reasons that people want to

try to improve sleep you would have

thought that we'd have known this you

know decades ago and it's a relevant

question to the point that you're asking

which is about these

carrots I know that there is still

probably some degree of a sleep loss

epidemic out there in the world there is

still that sleep machismo mentality that

I can sleep when I'm dead so how can we

try to motivate people well I can do it

with the stick and I can do the whole

sort of you know if it bleeds it leads

and do the Doomsday stuff and that can

that can motivate but why don't I try to

understand what it would be for most

people that would have them try to enact

better sleep behaviors

and they asked all sorts of different

options and the two things at the end of

the paper when they did all the

statistics that stood out like two sore

thumbs I want to try to improve my sleep

because I want to improve my mood I want

to improve my sleep because I want to

improve my body weight people know it

they already knew it we didn't have to

show them the data and so it's just

interesting so I'm just bringing those

two things up as a as carrot examples

there are many others of course too

terrific examples of carrots for uh that

one can get if they get adequate sleep

and we'll talk about quality and some

other features of sleep that are

important in just a moment but I'm

curious how come when we are sleep

deprived um we get bags under our eyes

and our skin Health shows it like even

one day you know if you know someone

well and you see them regularly and they

walk in and they they look particularly

well rested yeah we you know we think

they're you know kind of bright-eyed and

bushy tailed um so to speak um but you

can often see it in their skin and in

their eyes how glassy their eyes are how

open their eyes are but also the bags

under under their eyes and of course

folks um never say to somebody um you

look tired um it's it's a the other way

to um do it is just if if they look

particularly well rested on a given day

say you look well rested actually I told

you that today you did that's right I

would have forgot about that but now I

remember um and and it's true you look

very well rested being the the Sleep guy

and all um why do why do we show our

lack of sleep in our skin so rapidly

it's almost like a a thermometer on on

how much sleep somebody got the night

before it it's stunning isn't it and you

can almost see it you know if if you

have a partner and they come through to

the sort of kitchen in the morning and

they look at you and because you're so

familiar with that face because it's a

face that has imprinted on you thousands

of times you can notice subtle changes

and you can sometimes sense you know

they they do look tired but you're

absolutely right you don't you don't say

that you just say oh you know how are

you this morning and is there anything I

can do for you should I make you a

coffee maybe you should go back to sleep

and yeah yeah I think that's the that's

the politically incorrect indirect way

of saying boy do you look tired um two

things on that that front the first it

comes back to the immune system that

that sort of pale paror in a face almost

that sickly looking skin in PO is

because you're already seeing the

effects of the immune system and it's

the same with the bags under the eyes

that part of this reboot of the human

being you know that human beings seem to

have what I would describe as a recycle

rate and it seems to be about 16 hours

that after about 16 hours of wakefulness

we need about an 8 hourish and it's 7 to

n hours is the recommendation don't get

hung up on we'll speak about exactly

that in a second but it's that seems to

be required to reset this whole panoply

of of health and physiology of a of a

human being one of the things is the

immune system and you get this sickly

look about individuals and you get the

bags under the eyes so that in in part

explains it there was a great study done

by um a colleague of mine Tina sundelin

and um working out uh in Sweden uh at

the kolinska and this again was one of

those studies that I just thought was so

genius and it was a two-part study they

firstly took individuals and they sleep

deprived them for a night or they

allowed them to sleep well in fact they

went through both of those and after a

full night of sleep or after a night of

sleep deprivation they went into a

studio and they had the picture taken

they had a portrait shop done under

identical lighting conditions so now for

every participant in the study you've

got two head shots one of when they were

sleep deprived one when they were sleep

rested great now came the second part of

the experiment they then took all of

those kind of head shots and they

recruited a new set of participants who

acted as an independent set of judges

and those judges knew nothing about the

experimental conditions and the

manipulations that had just happened

they were simply shown these images and

they were asked to rate how attractive

does this person look how healthy does

this person look and how tired did does

this person look and again they knew

nothing about what was going on sure

enough with very high statistical

probability when the the head shot that

was taken when they were underslept they

rated that indiv idual as looking less

attractive as looking more sickly in

terms of their appearance and also

looking more tired so first they had