Sleep Is Your Superpower | Matt Walker | TED

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.