Sleep Is Your Superpower | Matt Walker | TED

Summary

In this enlightening talk, sleep expert Matt Walker reveals the profound impact of sleep on our health, highlighting how insufficient sleep can accelerate aging, impair memory, and even alter our DNA. He discusses the critical role of sleep for learning and memory, the alarming consequences of sleep deprivation on cognitive functions, and the potential for sleep to mitigate age-related cognitive decline and Alzheimer's disease. Walker also offers practical advice for achieving better sleep, emphasizing the importance of sleep as a nonnegotiable biological necessity for overall wellness.

Takeaways

• 😴 Lack of sleep can significantly affect male reproductive health, with men who sleep five hours a night having smaller testicles and lower testosterone levels compared to those who sleep seven hours or more.
• 🌙 Sleep deprivation can age a man's testosterone levels by a decade, and it also impairs female reproductive health equivalently.
• 📚 Sleep is essential for learning and memory; it helps to hit the 'save button' on new memories and prepares the brain to absorb new information effectively.
• 🧠 Sleep deprivation can lead to a 40% deficit in the brain's ability to form new memories, which is a significant impact on cognitive function.
• 💤 The hippocampus, acting as the brain's 'informational inbox,' is adversely affected by sleep deprivation, hindering the reception and retention of new memories.
• 🌪️ Deep sleep stages with sleep spindles are crucial for transferring memories from short-term to long-term storage, protecting them from being lost.
• 👴 Aging and sleep quality are interrelated, with poor deep sleep potentially contributing to cognitive decline in older adults and those with Alzheimer's disease.
• 🛠️ Non-pharmacological methods, such as direct current brain stimulation, can enhance deep sleep brainwaves and double the memory benefits from sleep.
• ❤️ Sleep loss has immediate effects on cardiovascular health, with a one-hour loss during daylight saving time correlating with a 24% increase in heart attacks the next day.
• 🛡️ Sleep restriction severely weakens the immune system, reducing natural killer cell activity by 70%, which is linked to an increased risk of various cancers.
• ⚠️ Sleep deprivation impacts gene activity, with 711 genes showing significant changes, including those related to immune function, tumor promotion, inflammation, and stress.

Q & A

What is the relationship between sleep duration and testicle size in men?

Men who sleep five hours a night have significantly smaller testicles than those who sleep seven hours or more.

How does sleep affect testosterone levels in men?

Men who sleep only four to five hours a night can have testosterone levels comparable to someone 10 years older, effectively aging them by a decade in terms of wellness.

Are there similar sleep-related effects on female reproductive health?

Yes, equivalent impairments in female reproductive health are caused by a lack of sleep.

Why is sleep important for learning and memory?

Sleep is crucial for learning and memory because it allows the brain to hit the 'save button' on new memories and prepares the brain to absorb new information, much like a dry sponge ready to soak up water.

What was the result of the study comparing memory formation in sleep-deprived individuals versus those who had a full night's sleep?

The study found a significant 40-percent deficit in the ability of the brain to make new memories without sleep.

What role does the hippocampus play in memory?

The hippocampus acts as the 'informational inbox' of the brain, receiving and holding onto new memory files.

How does deep sleep benefit memory and learning?

Deep sleep involves powerful brainwaves and sleep spindles that act like a file-transfer mechanism, moving memories from short-term to long-term storage, protecting them and making them safe.

What is the connection between sleep disruption and cognitive decline in aging and Alzheimer's disease?

Disruption of deep sleep is an underappreciated factor contributing to cognitive and memory decline in aging and Alzheimer's disease.

How does the speaker's sleep center approach improving sleep quality to combat cognitive decline?

The sleep center is developing a method called direct current brain stimulation, which amplifies deep-sleep brainwaves and nearly doubles the memory benefit from sleep.

What impact does sleep loss have on the immune system?

Sleep loss significantly reduces the activity of natural killer cells, which are crucial for identifying and eliminating dangerous elements like cancerous tumors, leading to a state of immune deficiency.

What are the long-term health risks associated with chronic sleep deprivation?

Chronic sleep deprivation is linked to an increased risk of developing various forms of cancer, cardiovascular disease, and even alterations in gene activity related to immune function and tumor promotion.

What advice does the speaker give for improving sleep quality?

The speaker advises maintaining regular sleep and wake times, regardless of the day, and keeping the bedroom cool, aiming for a temperature around 65 degrees Fahrenheit or 18 degrees Celsius.

Why is sleep considered a 'nonnegotiable biological necessity'?

Sleep is a nonnegotiable biological necessity because it serves as a life-support system, affecting every aspect of our health and well-being, and is essential for cognitive function, physical health, and even genetic stability.

What should one do if they are unable to sleep and remain awake in bed for too long?

If one is unable to sleep and stays awake in bed for too long, they should get out of bed and go to a different room to do something different, to avoid associating the bedroom with wakefulness.

Outlines

00:00

💤 Sleep and Reproductive Health

The speaker begins with a humorous yet serious note on the impact of sleep on reproductive health, highlighting that men who sleep only 4-5 hours a night have smaller testicles and lower testosterone levels compared to those who sleep 7 hours or more. This lack of sleep is equated to aging a man by a decade in terms of wellness. The speaker also points out that women experience similar impairments in reproductive health due to insufficient sleep, setting the stage for a discussion on the broader consequences of sleep deprivation on both brain and body.

05:00

📚 Sleep and Cognitive Function

This section delves into the critical role of sleep for learning and memory. The speaker explains that sleep is essential not only to consolidate new memories but also to prepare the brain for learning. Without adequate sleep, the brain's memory circuits become less efficient, impeding the absorption of new information. A study is referenced where individuals were divided into a sleep group and a sleep deprivation group, with the latter showing a 40% deficit in memory formation. The hippocampus, likened to the brain's 'informational inbox,' is highlighted as a key structure affected by sleep deprivation, with its function significantly reduced in those who are sleep-deprived.

10:03

🧠 Sleep, Aging, and Dementia

The speaker discusses the relationship between sleep, aging, and dementia. It is noted that deep sleep quality deteriorates with age, which is associated with cognitive decline. Recent evidence suggests that poor deep sleep may be a contributing factor to memory decline in aging and Alzheimer's disease. The potential for intervention is introduced, with the speaker describing a non-pharmacological approach using direct current brain stimulation to enhance deep sleep brainwaves and improve memory consolidation in young adults, offering hope for potential applications in older adults and dementia patients.

15:03

🛌 Sleep and Physical Health

This paragraph addresses the impact of sleep on physical health, starting with the effects on the immune system. Sleep deprivation is shown to significantly reduce the activity of natural killer cells, crucial for identifying and eliminating harmful elements like cancerous cells. The speaker also touches on the broader implications of sleep loss, such as increased risks of heart attacks, car crashes, and other health issues. The discussion then shifts to the genetic level, where sleep deprivation is found to alter the activity of numerous genes, some of which are linked to immune deficiency, tumor promotion, chronic inflammation, and stress-related cardiovascular diseases.

🌙 The Importance of Sleep Regularity and Temperature

The speaker concludes with practical advice on improving sleep quality, emphasizing the importance of regularity in sleep schedules and maintaining a cool sleeping environment. The ideal bedroom temperature for most people is suggested to be around 65 degrees Fahrenheit (18 degrees Celsius). The speaker reinforces the message that sleep is a vital biological necessity, not a lifestyle choice, and calls for a societal reevaluation of sleep as a critical component of health and well-being.

🛌 Sleep Deprivation and Coping Strategies

In a follow-up dialogue, the speaker addresses the issue of sleep deprivation and offers strategies for dealing with sleepless nights or shift work. It is emphasized that sleep cannot be 'banked' and must be prioritized. For those who find themselves awake in bed, the advice is to leave the bedroom and engage in a different activity to break the association of the bedroom with wakefulness, returning to bed only when feeling sleepy.

Keywords

💡Testicles

In the context of the video, 'testicles' is used to refer to a part of the male reproductive anatomy. The script suggests that the size of a man's testicles can be significantly influenced by the amount of sleep they get, with those who sleep five hours a night having smaller testicles than those who sleep seven hours or more. This concept is introduced to highlight the profound impact of sleep on overall health and wellness.

💡Testosterone

Testosterone is a hormone that plays a crucial role in the development of male reproductive tissues and secondary sexual characteristics. In the video, it is mentioned that men who sleep only four to five hours a night have testosterone levels comparable to those of someone 10 years older, indicating that sleep deprivation can accelerate the aging process in terms of hormone levels, which is critical for the video's theme of sleep's impact on health.

💡Sleep deprivation

Sleep deprivation refers to the condition of not getting enough sleep, which can have numerous negative effects on health. The video emphasizes that sleep deprivation can lead to a decline in both cognitive and physical health, affecting memory, immune function, and even genetic activity. It is a central theme of the video, illustrating the importance of adequate sleep for overall well-being.

💡Learning and memory

The video discusses the critical role of sleep in the functions of learning and memory. It explains that sleep is necessary after learning to consolidate new memories, and before learning to prepare the brain to absorb new information. The script uses the analogy of a 'dry sponge' to describe the brain's readiness to learn when well-rested, and the research presented shows the detrimental effects of sleep deprivation on memory formation.

💡Hippocampus

The hippocampus is a region in the brain that is essential for the consolidation of information from short-term to long-term memory. In the video, it is referred to as the 'informational inbox of the brain,' highlighting its role in receiving and holding onto new memory files. Sleep deprivation is shown to negatively affect the activity of the hippocampus, disrupting the memory consolidation process.

💡Deep-sleep brainwaves

Deep-sleep brainwaves, also known as delta waves, are the slowest type of brainwave and are associated with the deepest stages of sleep. The video explains that these brainwaves, along with sleep spindles, act as a file-transfer mechanism, moving memories from short-term to long-term storage. The quality of deep sleep and these brainwaves is crucial for memory protection and enhancement.

💡Sleep spindles

Sleep spindles are brief bursts of brain activity that occur during non-REM sleep and are associated with the deepening of sleep. The video describes them as 'spectacular bursts of electrical activity' that ride on top of deep-sleep brainwaves, contributing to the consolidation and protection of memories during sleep.

💡Aging and dementia

The video discusses the interrelation between aging, dementia, and sleep quality, particularly the decline in deep sleep that occurs as we age. It suggests that the disruption of deep sleep may be a contributing factor to cognitive and memory decline in aging and Alzheimer's disease. This concept is used to illustrate the broader societal and medical implications of sleep on cognitive health.

💡Natural killer cells

Natural killer cells are a type of white blood cell in the immune system that are capable of identifying and eliminating cancer cells and virally infected cells. The video emphasizes that sleep deprivation can significantly reduce the activity of these cells, leading to a compromised immune system and an increased risk of developing various forms of cancer.

💡Circadian rhythms

Circadian rhythms are the body's internal processes that follow a roughly 24-hour cycle, affecting sleep-wake patterns, hormone release, and other physiological functions. The video mentions the impact of daylight saving time on sleep, which disrupts these rhythms and can lead to an increase in heart attacks, car crashes, and other negative health outcomes.

💡Gene activity

Gene activity refers to the processes by which genes are expressed and carried out within a cell. The video presents research showing that sleep deprivation can alter the activity of hundreds of genes, some of which are related to immune function and others to the promotion of tumors and chronic inflammation. This highlights the far-reaching effects of sleep on the body's genetic regulation and health.

Highlights

Men who sleep five hours a night have significantly smaller testicles than those who sleep seven hours or more.

Sleep deprivation can age a man by a decade in terms of testosterone levels.

Lack of sleep causes equivalent impairments in female reproductive health.

Sleep is essential for learning and memory functions, acting as a 'save button' for new memories.

Sleep deprivation impairs the brain's ability to absorb new information.

A study found a 40% deficit in memory formation for those who stayed awake all night compared to those who slept.

The hippocampus, likened to the brain's 'informational inbox', shows reduced activity in sleep-deprived individuals.

Deep sleep brainwaves and sleep spindles are crucial for transferring memories from short-term to long-term storage.

Disruption of deep sleep is linked to cognitive decline in aging and Alzheimer's disease.

A method involving direct current brain stimulation during sleep can amplify deep-sleep brainwaves and double memory benefits.

Sleep loss is associated with a higher risk of heart attacks, car crashes, and even suicide rates.

Just one hour of sleep loss can significantly impact health outcomes, as seen with daylight saving time.

Sleep restriction to four hours for one night can lead to a 70% drop in natural killer cell activity.

Short sleep duration is linked to an increased risk for numerous forms of cancer.

Sleep deprivation can alter gene activity, with negative impacts on the immune system and promotion of tumors and chronic inflammation.

Regular sleep schedules and a cool sleeping environment are key for improving sleep quality.

Sleep is a nonnegotiable biological necessity, not a lifestyle luxury.

Sleep deprivation is a silent epidemic with catastrophic impacts on health and wellness.

Transcripts

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.