Sleep is your superpower

Sleep is your life-support system and Mother Nature's best effort yet at immortality, says sleep scientist Matt Walker. In this deep dive into the science of slumber, Walker shares the wonderfully good things that happen when you get sleep -- and the alarmingly bad things that happen when you don't, for both your brain and body. Learn more about sleep’s impact on your learning, memory, immune system and even your genetic code -- as well as some helpful tips for getting some shut-eye.

Thank you very much.

Well, I would like
to start with testicles.

(Laughter)

Men who sleep five hours a night

have significantly smaller testicles
than those who sleep seven hours or more.

(Laughter)

In addition, men who routinely sleep
just four to five hours a night

will have a level of testosterone

which is that of someone
10 years their senior.

So a lack of sleep
will age a man by a decade

in terms of that critical
aspect of wellness.

And we see equivalent impairments
in female reproductive health

caused by a lack of sleep.

This is the best news
that I have for you today.

(Laughter)

From this point, it may only get worse.

Not only will I tell you
about the wonderfully good things

that happen when you get sleep,

but the alarmingly bad things
that happen when you don't get enough,

both for your brain and for your body.

Let me start with the brain

and the functions of learning and memory,

because what we've discovered
over the past 10 or so years

is that you need sleep after learning

to essentially hit the save button
on those new memories

so that you don't forget.

But recently, we discovered
that you also need sleep before learning

to actually prepare your brain,

almost like a dry sponge

ready to initially soak up
new information.

And without sleep,
the memory circuits of the brain

essentially become
waterlogged, as it were,

and you can't absorb new memories.

So let me show you the data.

Here in this study, we decided
to test the hypothesis

that pulling the all-nighter
was a good idea.

So we took a group of individuals

and we assigned them
to one of two experimental groups:

a sleep group
and a sleep deprivation group.

Now the sleep group, they're going to get
a full eight hours of slumber,

but the deprivation group,
we're going to keep them awake

in the laboratory, under full supervision.

There's no naps or caffeine, by the way,
so it's miserable for everyone involved.

And then the next day,

we're going to place those participants
inside an MRI scanner

and we're going to have them
try and learn a whole list of new facts

as we're taking snapshots
of brain activity.

And then we're going to test them

to see how effective
that learning has been.

And that's what you're looking at
here on the vertical axis.

And when you put
those two groups head to head,

what you find is a quite significant,
40-percent deficit

in the ability of the brain
to make new memories without sleep.

I think this should be concerning,

considering what we know
is happening to sleep

in our education populations right now.

In fact, to put that in context,

it would be the difference
in a child acing an exam

versus failing it miserably -- 40 percent.

And we've gone on to discover
what goes wrong within your brain

to produce these types
of learning disabilities.

And there's a structure that sits

on the left and the right side
of your brain, called the hippocampus.

And you can think of the hippocampus

almost like the informational
inbox of your brain.

It's very good at receiving
new memory files

and then holding on to them.

And when you look at this structure

in those people who'd had
a full night of sleep,

we saw lots of healthy
learning-related activity.

Yet in those people
who were sleep-deprived,

we actually couldn't find
any significant signal whatsoever.

So it's almost as though sleep deprivation
had shut down your memory inbox,

and any new incoming files --
they were just being bounced.

You couldn't effectively
commit new experiences to memory.

So that's the bad that can happen
if I were to take sleep away from you,

but let me just come back
to that control group for a second.

Do you remember those folks
that got a full eight hours of sleep?

Well, we can ask
a very different question:

What is it about the physiological
quality of your sleep

when you do get it

that restores and enhances
your memory and learning ability

each and every day?

And by placing electrodes
all over the head,

what we've discovered
is that there are big, powerful brainwaves

that happen during
the very deepest stages of sleep

that have riding on top of them

these spectacular bursts
of electrical activity

that we call sleep spindles.

And it's the combined quality
of these deep-sleep brainwaves

that acts like a file-transfer
mechanism at night,

shifting memories from a short-term
vulnerable reservoir

to a more permanent long-term
storage site within the brain,

and therefore protecting them,
making them safe.

And it is important that we understand

what during sleep actually transacts
these memory benefits,

because there are real medical
and societal implications.

And let me just tell you about one area

that we've moved this work
out into, clinically,

which is the context of aging
and dementia.

Because it's of course no secret
that, as we get older,

our learning and memory abilities
begin to fade and decline.

But what we've also discovered

is that a physiological signature of aging
is that your sleep gets worse,

especially that deep quality of sleep
that I was just discussing.

And only last year,
we finally published evidence

that these two things,
they're not simply co-occurring,

they are significantly interrelated.

And it suggests
that the disruption of deep sleep

is an underappreciated factor

that is contributing
to cognitive decline or memory decline

in aging, and most recently
we've discovered,

in Alzheimer's disease as well.

Now, I know this is remarkably
depressing news.

It's in the mail. It's coming at you.

But there's a potential
silver lining here.

Unlike many of the other factors
that we know are associated with aging,

for example changes
in the physical structure of the brain,

that's fiendishly difficult to treat.

But that sleep is a missing piece
in the explanatory puzzle

of aging and Alzheimer's is exciting

because we may be able
to do something about it.

And one way that we are
approaching this at my sleep center

is not by using
sleeping pills, by the way.

Unfortunately, they are blunt instruments
that do not produce naturalistic sleep.

Instead, we're actually developing
a method based on this.

It's called direct current
brain stimulation.

You insert a small amount
of voltage into the brain,

so small you typically don't feel it,

but it has a measurable impact.

Now if you apply this stimulation
during sleep in young, healthy adults,

as if you're sort of singing in time
with those deep-sleep brainwaves,

not only can you amplify
the size of those deep-sleep brainwaves,

but in doing so, we can almost
double the amount of memory benefit

that you get from sleep.

The question now
is whether we can translate

this same affordable,
potentially portable piece of technology

into older adults and those with dementia.

Can we restore back
some healthy quality of deep sleep,

and in doing so, can we salvage
aspects of their learning

and memory function?

That is my real hope now.

That's one of our moon-shot
goals, as it were.

So that's an example
of sleep for your brain,

but sleep is just
as essential for your body.

We've already spoken about sleep loss
and your reproductive system.

Or I could tell you about sleep loss
and your cardiovascular system,

and that all it takes is one hour.

Because there is a global experiment
performed on 1.6 billion people

across 70 countries twice a year,

and it's called daylight saving time.

Now, in the spring,
when we lose one hour of sleep,

we see a subsequent 24-percent increase
in heart attacks that following day.

In the autumn,
when we gain an hour of sleep,

we see a 21-percent
reduction in heart attacks.

Isn't that incredible?

And you see exactly the same profile
for car crashes, road traffic accidents,

even suicide rates.

But as a deeper dive,
I want to focus on this:

sleep loss and your immune system.

And here, I'll introduce these delightful
blue elements in the image.

They are called natural killer cells,

and you can think of natural killer cells
almost like the secret service agents

of your immune system.

They are very good at identifying
dangerous, unwanted elements

and eliminating them.

In fact, what they're doing here
is destroying a cancerous tumor mass.

So what you wish for
is a virile set of these immune assassins

at all times,

and tragically, that's what you don't have
if you're not sleeping enough.

So here in this experiment,

you're not going to have your sleep
deprived for an entire night,

you're simply going to have your sleep
restricted to four hours

for one single night,

and then we're going to look to see
what's the percent reduction

in immune cell activity that you suffer.

And it's not small -- it's not 10 percent,

it's not 20 percent.

There was a 70-percent drop
in natural killer cell activity.

That's a concerning state
of immune deficiency,

and you can perhaps understand
why we're now finding

significant links between
short sleep duration

and your risk for the development
of numerous forms of cancer.

Currently, that list includes
cancer of the bowel,

cancer of the prostate
and cancer of the breast.

In fact, the link between a lack of sleep
and cancer is now so strong

that the World Health Organization

has classified any form
of nighttime shift work

as a probable carcinogen,

because of a disruption
of your sleep-wake rhythms.

So you may have heard of that old maxim

that you can sleep when you're dead.

Well, I'm being quite serious now --

it is mortally unwise advice.

We know this from epidemiological studies
across millions of individuals.

There's a simple truth:

the shorter your sleep,
the shorter your life.

Short sleep predicts all-cause mortality.

And if increasing your risk
for the development of cancer

or even Alzheimer's disease

were not sufficiently disquieting,

we have since discovered
that a lack of sleep will even erode

the very fabric of biological life itself,

your DNA genetic code.

So here in this study,
they took a group of healthy adults

and they limited them
to six hours of sleep a night

for one week,

and then they measured the change
in their gene activity profile

relative to when those same individuals

were getting a full eight hours
of sleep a night.

And there were two critical findings.

First, a sizable and significant 711 genes

were distorted in their activity,

caused by a lack of sleep.

The second result
was that about half of those genes

were actually increased in their activity.

The other half were decreased.

Now those genes that were switched off
by a lack of sleep

were genes associated
with your immune system,

so once again, you can see
that immune deficiency.

In contrast, those genes
that were actually upregulated

or increased by way of a lack of sleep,

were genes associated
with the promotion of tumors,

genes associated with long-term
chronic inflammation within the body,

and genes associated with stress,

and, as a consequence,
cardiovascular disease.

There is simply no aspect of your wellness

that can retreat at the sign
of sleep deprivation

and get away unscathed.

It's rather like a broken
water pipe in your home.

Sleep loss will leak down
into every nook and cranny

of your physiology,

even tampering with
the very DNA nucleic alphabet

that spells out
your daily health narrative.

And at this point, you may be thinking,

"Oh my goodness,
how do I start to get better sleep?

What are you tips for good sleep?"

Well, beyond avoiding
the damaging and harmful impact

of alcohol and caffeine on sleep,

and if you're struggling
with sleep at night,

avoiding naps during the day,

I have two pieces of advice for you.

The first is regularity.

Go to bed at the same time,
wake up at the same time,

no matter whether
it's the weekday or the weekend.

Regularity is king,

and it will anchor your sleep

and improve the quantity
and the quality of that sleep.

The second is keep it cool.

Your body needs to drop
its core temperature

by about two to three degrees
Fahrenheit to initiate sleep

and then to stay asleep,

and it's the reason
you will always find it easier

to fall asleep in a room that's too cold

than too hot.

So aim for a bedroom temperature
of around 65 degrees,

or about 18 degrees Celsius.

That's going to be optimal
for the sleep of most people.

And then finally,
in taking a step back, then,

what is the mission-critical
statement here?

Well, I think it may be this:

sleep, unfortunately,
is not an optional lifestyle luxury.

Sleep is a nonnegotiable
biological necessity.

It is your life-support system,

and it is Mother Nature's
best effort yet at immortality.

And the decimation of sleep
throughout industrialized nations

is having a catastrophic impact
on our health, our wellness,

even the safety and the education
of our children.

It's a silent sleep loss epidemic,

and it's fast becoming one of the greatest
public health challenges

that we face in the 21st century.

I believe it is now time for us
to reclaim our right

to a full night of sleep,

and without embarrassment

or that unfortunate stigma of laziness.

And in doing so, we can be reunited
with the most powerful elixir of life,

the Swiss Army knife
of health, as it were.

And with that soapbox rant over,

I will simply say, good night, good luck,

and above all ...

I do hope you sleep well.

Thank you very much indeed.

(Applause)

Thank you.

(Applause)

Thank you so much.

David Biello: No, no, no.
Stay there for a second.

Good job not running away, though.
I appreciate that.

So that was terrifying.

Matt Walker: You're welcome.
DB: Yes, thank you, thank you.

Since we can't catch up on sleep,
what are we supposed to do?

What do we do when we're, like,
tossing and turning in bed late at night

or doing shift work or whatever else?

MW: So you're right,
we can't catch up on sleep.

Sleep is not like the bank.

You can't accumulate a debt

and then hope to pay it off
at a later point in time.

I should also note the reason
that it's so catastrophic

and that our health
deteriorates so quickly,

first, it's because human beings
are the only species

that deliberately deprive
themselves of sleep

for no apparent reason.

DB: Because we're smart.

MW: And I make that point
because it means that Mother Nature,

throughout the course of evolution,

has never had to face the challenge
of this thing called sleep deprivation.

So she's never developed a safety net,

and that's why when you undersleep,

things just sort of implode so quickly,
both within the brain and the body.

So you just have to prioritize.

DB: OK, but tossing and turning in bed,

what do I do?

MW: So if you are staying in bed
awake for too long,

you should get out of bed
and go to a different room

and do something different.

The reason is because your brain
will very quickly associate your bedroom

with the place of wakefulness,

and you need to break that association.

So only return to bed when you are sleepy,

and that way you will relearn
the association that you once had,

which is your bed is the place of sleep.

So the analogy would be,

you'd never sit at the dinner table,
waiting to get hungry,

so why would you lie in bed,
waiting to get sleepy?

DB: Well, thank you for that wake-up call.

Great job, Matt.

MW: You're very welcome.
Thank you very much.