A good night's sleep has perhaps never been more important. Sharing wisdom and debunking myths, sleep scientist Matt Walker discusses the impact of sleep on mind and body -- from unleashing your creative powers to boosting your memory and immune health -- and details practices you can start (and stop) doing tonight to get some rest. (This virtual conversation is part of the TED Connects series, hosted by head of TED Chris Anderson and current affairs curator Whitney Pennington Rodgers. Recorded April 1, 2020)

And a really important conversation today, I think, because I don't know about you, Whitney, but there have been nights in the last couple of weeks where I just haven't slept that well.

There's just a lot of stress, there's a lot of worry, there's a lot of uncertainty and so forth.

I feel like my sleep has been a little less than ideal lately, for sure.

Probably for a lot of you out there, too, I'd imagine.

So we're very lucky to have with us today the perfect speaker for this.

He's a professor of neuroscience and psychology at Berkeley in California and director of the Center for Human Sleep Science, author of a book 3 years ago, why we sleep, and last year gave a TED talk and it's been seen nearly 10 million times now.

So it's a treat to invite here Matt Walker.

Whitney will be back with questions from you all in a bit.

I mean, I guess that's going to be the first question on top of people's minds is, you know, is there a case that sleep matters now more than ever?

I think, firstly, it's important for me to not necessarily feed into people's anxiety regarding sleep.

I know, as you mentioned, that sleep is difficult for some people when anxiety is high and of course that's never more so at present.

So what I would say is that if anything that we're talking about feels as though it's a trigger, feel free just to come back at a time that feels better in terms of that anxiety level.

In terms of sleep and COVID-19, right now, we don't necessarily have any evidence to suggest that there is some kind of a link between those 2.

But certainly, what we know is that there is a very intimate relationship between your sleep health and your immune health.

And I'll give you just a couple of examples.

There was a study some years ago that demonstrated that individuals who reported getting less than 7 hours of sleep had almost a threefold increased likelihood of becoming infected by the rhinovirus, which is what we all think of as the common cold, relative to those who were getting 8 hours of sleep or more.

There was another study in over 50, 000 women, And what they found was that individuals who were getting 5 hours of sleep or less had a

increased risk for developing pneumonia, which is a respiratory lung infection, relative to those who are getting 8 hours of sleep or more.

But I think perhaps 1 of the most striking results in this relationship between sleep and immune health was a study where they demonstrated if you're not getting sufficient sleep in the week before you get your flu shot, you produce less than 50 percent of the normal antibody response, therefore rendering that vaccination significantly less effective.

So I think, particularly actually on that last point, at some point, we will develop a vaccine for COVID-19.

And then the question becomes, is the same thing true?

If you're not getting the sleep that you need in the week before you get your COVID shot, will that immunization become significantly less effective?

I actually think that's an important question that we will need to answer in the future.

But given that, In a way, if someone gets infected, there follows this sort of epic battle between a virus and their immune system.

It's obvious common sense to give your immune system every shot it can, every chance it can.

And in many other cases, Sleep is known to do that.

CAO HINTONS I think certainly, from an immune health perspective, we know that sleep essentially sharpens every tool in that box.

Sleep essentially restocks the weaponry in your immune arsenal, giving you the greatest chance to fight off infection.

And I think, as of at least April 2020, we don't have that evidence yet.

I know that there are a number of studies, however, that are looking at that.

Even some of the sleep-tracking companies are trying to rally efforts around that and examine this right now.

CA Well, a little later in this interview, we're going to dig into how to sleep better.

I know you've got a lot of interesting advice in that regard.

But before we go there, let's spend a bit more time thinking about the different ways that sleep can be really helpful now, because paradoxically, we actually, many of us, have, in theory at any rate, more time to sleep than we've ever had.

And so, boy, if we could put that to use.

How else could it help us, just during our waking day and the things that we're having to focus on now?

Sleep seems to provide a benefit to almost every major organ system in the body and many of the operations of the mind.

And perhaps I'll just give 2 examples within the mind.

1 of the things that we know sleep is essentially incredibly beneficial for is learning memory and even creativity.

And when it comes to memory, sleep is important in perhaps at least 3 ways.

Firstly, we know that you need sleep before learning to actually prepare your brain, a little bit like a dry sponge ready to initially absorb new memories and lay down those new memory traces.

You not only need sleep before learning to imprint those memories into the brain, you also need sleep after learning to essentially cement those new memories into the neural architecture of the brain so that you don't forget.

And certainly there's very good evidence for that.

In fact, sleep almost performs a file transfer mechanism where it takes memories and shifts them from a sort of a short-term vulnerable reservoir to a more permanent long-term storage site within the brain.

And that's what we used to think that sleep was beneficial for, taking individual memories and holding onto them, as it were, future-proofing that information.

But we've since discovered that sleep is actually much more intelligent than that.

Sleep will actually take new memories and start to integrate and associate them with pre-existing stores of information.

So it's almost a little bit like memory alchemy at night, so that you wake up the next day with a revised mind-wide web of associations.

And that leads to remarkable states of creativity.

Studies in the laboratory showing that sleep can inspire almost a threefold increase in creative insights.

And it's probably the reason that, you know, you've never been told to stay awake on a problem, but instead, you're told to sleep on a problem.

And I think that phrase seems to exist in almost every language that I've inquired about to date, which means that this creative benefit of sleep transcends cultural boundaries.

CAO): That is 1 of the most mind-boggling things to me, about how you can be worried or puzzled about something, and you wake up in the middle of the night, and suddenly, you know, possibilities pop into place.

And the fact that you're --" In 1 way, it's kind of annoying, because it means your unconscious mind has been there somehow, with the benefit of sleep, I guess, pre-associating and doing things that you were supposed to do all by yourself, and it's not fair.

And so you're saying that there's, like, the 3 times the creative output, I'm very curious as to how that's measured, but I mean, that's an amazing claim, if you have enough sleep.

CA2C3D4L4E4L Yeah, so there's a lovely study done by some German researchers a couple of years ago, and the way that they did this, they gave people a series of problems that had a hidden embedded rule into it, and they never told them about that rule.

But through exposure, perhaps gradually you can divine that hidden insight that is sort of locked into that problem.

And then they bring them back, and then they test them at some point later to see if the light bulb moment has gone on for those individuals, and they've defined that sort of creative solution, that hidden rule.

And you can do that after being awake, or you can do that after being asleep.

And that's how they can start to tease apart, is it just time that the brain needs for creativity?

And it was time asleep that seemed to gift the brain this sort of creative genius ability.

And I think something else you mentioned there that's interesting, too.

It's not just creativity, but sleep can also, I think, change our emotional and mood state, sort of feeling better the next day.

And that's what we're now starting to learn is another function of sleep for the mind.

That sleep provides almost a form of overnight therapy, that sleep will take those difficult, stressful situations or problems.

And sleep almost acts like a nocturnal soothing balm, just sort of taking the sharp edges off our emotional experiences, so that we come back the next day and we don't feel as challenged or as triggered by those events anymore.

So it's not necessarily, I think, time that heals all wounds.

It's time with a night of sleep that provides that form of emotional convalescence.

And that's perhaps particularly important in this modern era.

I think there's a lovely quote by the American entrepreneur Joseph E.

Kosman, and he said, the best bridge between despair and hope is a good night of sleep.

And I think that's particularly prescient right now.

CA You can certainly imagine that a lot of people right now are wrestling with various mental health issues that are possibly exacerbated by the state that we're in.

And I guess what I'm hearing you saying is, don't forget the simplest therapy of all, which is to sleep enough that that in itself may help.

Ph.D., Psychologist, University of Oxford Sleep, I think, we're learning, performs a form of emotional first aid, as it were.

And it reminds me actually of another lovely phrase by Charlotte Bronte, who said that a ruffled mind makes for a restless pillow.

And I think we've all had that experience of feeling sort of triggered that day and we just know that sleep isn't necessarily going to come at night.

Yeah, I was just going to say, I think it's part of the reason that we're finding that sleep is so tied into psychiatric disorders and mental health conditions.

In the past 20 years, for example, we've not been able to discover a single psychiatric condition in which sleep is normal.

So I think sleep has a very powerful story to tell in our understanding and probably treatment of serious mental illness.

There's another issue that I suspect a lot of people are wrestling with right now, is that a lot of people's response to being isolated and feeling a bit stressed is to imagine more and more delicious things to eat and cook as we go to comfort food.

And so some people, if they may wrestle with weight issues even more now than normal.

I think you've argued that sleep has a role to play in the battle against gaining weight.

And I think, very understandably right now, that may also be relevant.

We know how this mechanism plays out, where if we're not sleeping well, we can start to gain weight.

The first piece of evidence concerns hormones, and 2 specific hormones that control our hunger levels.

Those 2 hormones are called leptin and ghrelin.

And I often say that they almost sound like hobbits, but I promise you they're not.

Now, leptin, when it's released, is the signal to your brain to say you're full, you're satiated, you don't want to eat anymore.

It says you're not full, you're not satisfied with your food, you should eat more.

And when we start to under sleep, those 2 hormones go in opposite directions.

We lose the signal that says you're full and you're satisfied with your meal, which is leptin, but we increase the hormone that says, no, you're actually hungry.

Even though you've just eaten, you should eat more.

And so as a consequence, people who are underslept can start to eat somewhere between 2 to 400 extra calories per day when you look at some of these studies.

It's not, by the way, just that you start to eat more.

It's also that when you are underslept, your preference for different food groups actually shift.

And so you start to desire more heavy-hitting carbohydrates and more simple, processed, sugary foods, rather than those more healthy macro ingredients, which also sort of sets you on a path towards a more, what we call, obesogenic profile.

But it also actually changes how your brain operates in response to food.

And we did a study a couple of years ago where we gave people a good night of sleep, or we kept them awake for a night, and then we placed them inside an MRI scanner, and we showed them different types of food groups, things that were very desirable, ice cream, chocolate, etc., or sort of healthy, leafy greens.

And what we found is that when people were not getting the sleep that they needed, the sort of deep, hedonic centers of the brain were actually ramped up in response to desirable foods, and they started to want those more unhealthy foods.

And this in part was because the frontal lobe in their brain, which almost acts like this sort of CEO of the brain, regulating and controlling our impulses and our emotions, that was actually switched off by a lack of sleep.

And so now you start to reach for those unhealthy food choices.

But I think we can think of that more positively and say, perhaps sleep can actually be a tool in your box that can enable you to manage your weight more efficiently and correctly.

And so getting that extra sleep should lead to, and that's what we see in the data, a healthier profile of body weight.

Yeah, I suspect, speaking personally, there's no amount of sleep I could have that could make me lust after broccoli.

But let's bring you into the sleep laboratory, and I'll order some broccoli and some oregano.

Actually, char-grilled with a bit of olive oil and salt, it's not so bad.

So someone listening to this, if you were trying to take a positive stance of this isolation time or whatever, thought, you know, I'm going to make this a time of learning and of creativity and so forth.

I mean, that's a possibility for someone.

What you're saying is, don't forget if you're going to do that, don't forget to make sleep a key part of that program.

That's right, and it is a time like no other where I think we have, in some ways, more sleep opportunity time.

And in fact, there was a recent report out.

And it's not a scientific report, so we have to be careful not to over-interpret it.

And they looked at 68, 000 Americans and using sleep tracker data, sort of wearable tracker data.

And they looked at the change in sleep since March 13th, which was when the president mandated a national state of emergency.

And what they demonstrated or suggested was that since then, there's actually been almost a 20% increase in sleep time on average as a nation here in the United States.

Now, again, I think we have to be very careful.

It could be that people are just sort of sitting in bed and you know working or watching television in the evening.

But even if it's half that amount, I think what it may tell us is that this time, this very strange era that we're living in right now, has unmasked what is otherwise a chronic persistent debt in our sleep.

And finally, you know, when you remove the brakes on sleep you can see that sleep flourishes in return.

Now I'm not suggesting that that's true of everyone.

I think when we look at that data more closely, we'll probably see 2 clouds of data.

1 cloud of data where people are perhaps sleeping more, but then there will be this opposite cloud where people actually are sleeping significantly less because of the things that we've spoken about.

Anxiety about the virus itself, concerns for example about whether they all hold their jobs, and people, of course, magically have lost their job.

And so I think we'll see shifts, but that seems to be an interesting trend.

I was having a conversation with friends last night about how surprising the final health statistics coming out of this whole thing may look.

Because if people, A, have more sleep, B, are being isolated, so they're not catching all the other diseases they might be getting.

I think flu stats are way down compared to a typical year at this point, partly because of the isolation.

Less road deaths, less who knows what else.

I mean, just possibly there'll be some compensation for the horrifying death rates that we're going to see from COVID.

But it's so interesting trying to put those pieces together.

And here's what is also interesting to me.

Like, 1 of the key symptoms of this virus is to make people incredibly tired, like a fever and incredibly tired.

And it's striking to me that, in principle, we see those things as these awful things that happen, that those are the virus's weapons.

There are bodies' weapons to try to beat the virus.

That's the body's natural response with a lot of pathogens.

And with sleep, should we just view, like, if you're having symptoms and you're feeling really tired, does it help at all to say, this isn't the bug, this is me, and to listen to your body and to get all the sleep you damn well can?

CA I think it's a beautiful example, and it's another demonstration of that relationship that we spoke about.

I think everyone knows that when you get sick or you get a common cold, what you really want to do is just curl up in bed and sort of sleep it off, as it were.

And in fact, we understand that relationship that when you become infected there are a set of changes in immune factors that only go to work to try and fight these infections But they actually will signal to sleep that sleep in terms of its duration is needed in greater amounts.

And in fact, there are immune factors that are sleep stimulating factors because the body knows that the best effort, sort of the most powerful healthcare system that it can call up in its weaponry defense against infection is this thing called sleep.

And that's why we actually feel as though we want to sleep more.

It's not just because we're at home and we're not at work and we have the chance to sleep more, it's that your immune system is actually co-opting and bringing sleep into the equation to help fight that infection, because sleep is so powerful in that regard.

CA So given all these reasons why we need more sleep now than ever, perhaps.

What are your top tips on how someone can get a really great night's sleep?

Yeah, I think beyond the typical, what we call, sleep hygiene factors, such as controlling your light in the evening, making your room a cool place, also being mindful of caffeine and alcohol.

I could give 3 tips for what to do if you've had a bad night of sleep, and then if you're still struggling with sleep, 3 tips for perhaps how to better manage that.

So firstly, if you're coming off a bad night of sleep, The first thing, and this may sound counterintuitive, particularly coming from someone like me, is not to sleep in the next day.

And there are 2 specific reasons for that.

Firstly, your body has a 24-hour clock, and it expects regularity, and it thrives best on regularity.

And if you start to change your wake-up time, you will confuse that 24-hour clock.

Wake up at the same time, even after a bad night of sleep.

The other reason is that if you sleep in late, you're probably not going to feel sleepy until later that following evening.

So once again, you start to drift forward in time.

The second piece of advice there relates to that.

Don't necessarily go to bed any earlier than you would otherwise, because sometimes if you do that, even if you're feeling quite sleepy, you can then lie in bed and you can start to toss and turn.

So try to push through until your standard bedtime that following evening.

The final piece of advice after a bad night of sleep is resist the urge to nap during the day.

Now if you are a healthy good sleeper and you can nap regularly, then naps are just fine.

But if you are struggling with sleep and have had a bad night of sleep, try not to nap, especially late in the afternoon.

Because you can think of naps in that situation almost like snacking before a main meal.

If you have a snack, you're not going to have the same appetite to try and sort of consume that main meal.

And the same is true if you start to snack with a nap just before your main sleep.

What to do if you are still struggling with sleep?

I think the first thing is, if you're in bed and you've been awake for, let's say, 20 or 30 minutes, perhaps, the advice is take a break.

Stop trying to fight sleep, because typically the harder that we try to force ourselves to sleep, the more stressed and anxious that we become, and the further that we push sleep away from us.

And, you know, it's a little bit like trying to remember a name where you're sort of the harder you think, the less likely it is that you are to recall that name.

Again, I think the advice here 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?

Just get out of bed, go and do something different in dim light, read a book, listen to a podcast, only return to bed when you're sleepy, and that way you'll relearn the association that your bed is the place of sleep.

Yeah, My voice, I think, and my inane words are usually the best sort of soporific known to women and men.

I think the last 2 pieces of advice beyond, and that really is a powerful 1, is just please stop, give yourself a break and stop trying.

That can be really helpful because otherwise if you're in bed, you're stressed and ruminated, you're teaching your brain that this thing called the bed is the place where you wake up.

Instead, you retrain it to, when you return, understand that the bed is the place where you always sleep and you have confidence in sleeping.

The last 2 pieces of advice have a wind down routine.

I think many of us have this idea that sleep perhaps should be like a light switch that we get into bed and we can just go from a 1 to a 0, that it's a binary, that we can just switch off and instantly fall asleep.

Sleep is much more like trying to land a plane, that you've got to gradually give it time to descend down onto that terra firma of good sleep.

And the faster that you're going in terms of the mind, the longer that you need to give the mind to sort of gradually come back down into sleep.

Also taking a hot bath or a shower, having some kind of ritual.

And that's useful, by the way, not just because a hot bath will relax you, but we also have this science in sleep called the warm bath effect, where as you come out of the bath, all of the blood has come to the surface of your skin, and when you get out, you radiate all of the heat out of your body, so your core body temperature actually drops, and that's actually good for sleep.

It helps you fall asleep faster and stay asleep and more deeply.

The last quick point I would make if you are struggling with sleep, and it's a simple tip but can be effective, remove all clock faces from the bedroom.

It's fine to have an alarm clock, but try to take away any information about time.

Because if you're struggling with sleep, knowing that it's 2.15 a.m.

The last thing I would note, by the way, is that if these things are not working well for you, and this is a tip from a wonderful sleep clinician called Michael Grandner, if I'm an athletic coach trying to give you tips for improvement, but you have a sprained ankle, then nothing I can tell you is going to be useful until you fix that, that sprained ankle.

And what I mean here is that if these things aren't working for you, it could be that you have an underlying sleep disorder.

And if that's the case, These tips really aren't going to be effective until you go and connect with a doctor and see if you have an underlying sleep disorder that has been undiagnosed.

So there are a lot of people chiming in with questions all over the world.

And it's like there are a number of our viewers who are really appreciating what you're saying and are struggling with sleep themselves.

And 1 of the questions we've seen is around stress as it relates to our sleep cycles and our dreams also.

Just what impact can stress have on the kinds of dreams we have and our sleep cycles in general?

So stress within the body causes a number of different changes.

1 of the things that stress will do is elevate a hormone called cortisol, which is often thought of as not just an activating hormone but also a stress-related hormone.

And typically, as we try to fall asleep, cortisol should actually be decreasing beautifully, and it should fall to almost its lowest point right around the time when we're trying to fall asleep.

And so if we're stressed and if you in fact look at the disorder of insomnia, people start to decline in their cortisol like a healthy sleeper would do, but just around the bedroom period where you're starting to think about going to sleep, cortisol actually starts to spike back up again, and that can prevent people from falling asleep.

So cortisol is 1 of the ingredients that can impact our sleep and our sleep cycles.

The other factor is the nervous system in the body.

And in fact, we have 2 branches of your automatic nervous system.

We have the fight or flight branch, and then we have the more calming, what we call the rest or digest branch of the nervous system.

And when we become stressed and anxious, we shift over more into that sort of fight or flight situation of the nervous system.

And we also know that that needs to dampen down in order to stay asleep.

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Why sleep matters now more than ever