Why Do We Need Sleep?

Originally published on November 3, 2017 10:22 am

Part 2 of the TED Radio Hour episode Maslow's Human Needs

About Russell Foster's TED Talk

What do we know about one of our most basic needs: sleep? Not a lot, says circadian neuroscientist Russell Foster. We know we need to do it to stay alive, but much about it remains a mystery.

About Russell Foster

Russell Foster is Professor of Circadian Neuroscience and the Head of the Department of Ophthalmology at the University of Oxford. Foster studies sleep and its role in our lives, examining how our perception of light influences our sleep-wake rhythms.

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GUY RAZ, HOST:

We'll hear more from Margie Lachman later on. And as she mentioned, the first and most fundamental needs in Maslow's hierarchy were physiological needs - food, water, shelter and a need that most of us just don't treat like one...

RUSSELL FOSTER: ...Sleep. Sleep has to be absolutely at the top of that hierarchy, in a sense.

RAZ: This is Russell Foster. He's a circadian neuroscientist at Oxford University, where he studies sleep. And in his research he's discovered that most people don't take it as seriously as they should.

FOSTER: I think it's the apparent, you know, dilemma that we don't seem to be doing anything. We seem to be just essentially wasting our time while we're asleep. So when you celebrate your 60th wedding anniversary, it's worth reflecting that of those 60 years, 21-and-a-half were probably asleep.

RAZ: Wow.

FOSTER: Therefore, it's perhaps only reasonable to celebrate 38-and-a-half years. But the key thing is that the quality of that 21-and-a-half years spent asleep will to some extent dictate the quality of those years awake with your partner.

RAZ: Of course, why exactly sleep is so important and what's going on when we do it is still largely a mystery to scientists like Russell. But there are a lot of theories out there, and Russell Foster described three of them in his TED Talk.

(SOUNDBITE OF TED TALK)

FOSTER: The first is sort of the restoration idea. And it's somewhat intuitive. Essentially, all the stuff we've burnt up during the day, we restore, we replace, we rebuild during the night. And indeed, as an explanation it goes back to Aristotle, so that's - what? - 2,300 years ago. It's fashionable at the moment because what's been shown is that within the brain a whole raft of genes have been shown to be turned on only during sleep. And those genes are associated with restoration and metabolic pathways. So there's good evidence for the whole restoration hypothesis.

What about energy conservation? You essentially sleep to save calories. When you do the sums, though, it doesn't really pan out. The energy-saving of sleeping is about 110 calories a night. Now, that's the equivalent of a hotdog bun, so I'm less convinced by the energy conservation idea.

But the third idea I'm quite attracted to, which is brain processing and memory consolidation. What we know is that if after you've tried to learn a task and you sleep-deprive individuals, the ability to learn that task is smashed. It's really, hugely attenuated. So sleep and memory consolidation is also very important. However, it's not just the laying down a memory and recalling it. What's turned out to be really exciting is that our ability to come up with novel solutions to complex problems is hugely enhanced by a night of sleep. In fact, it's been estimated to give us a threefold advantage. Sleeping at night enhances our creativity. And what seems to be going on is that in the brain those neural connections that are important, those synaptic connections that are important, are linked and strengthened, while those that are less important tend to sort of fade away and be less important.

RAZ: And so, when we sleep, parts of us are shutting down. But actually, big parts of our system never sleep, never shut down. They're constantly working, right?

FOSTER: No, no. And in fact that's very important because one of the ways that we sort of thought about it is that we've got all these jigsaw pieces flowing in during the day, that the brain is essentially having to deal with billions of bits of information. And we haven't had time to sort of put it into the rest of the jigsaw puzzle. But at night you've got that time to try and associate those bits of the jigsaw puzzles, those new pieces of the puzzle, in with what you've experienced previously and what you might anticipate happening in the future.

RAZ: So all life on Earth has an innate sense of time. In mammals, the queue of course is light. It's what determines our circadian rhythms. And researchers, like Russell, are starting to better understand the neurological and physiological impact of what happens when we ignore those rhythms and don't get enough sleep, which accounts for most of us.

FOSTER: And that's across the age spectrum, from teenagers, stressed adults, indeed the retired population.

RAZ: And not getting enough makes you less alert, more irritable, prone to illness. And if you're sleep deprived...

FOSTER: You're releasing one of the hunger hormones called ghrelin, and that enormously increases your appetite for carbohydrates, and particularly sugars.

RAZ: Lack of sleep hurts your memory. It affects your judgment. But perhaps most importantly, lack of sleep hurts your body's ability to defend itself.

FOSTER: So, for example, even one night of no sleep can reduce elements of your immune system by about 24, 25 percent.

RAZ: And Russell says in lab experiments, when mice are sleep deprived, they don't die of exhaustion. They actually die from infections.

FOSTER: And one of the problems of not having enough sleep is that we are very poorly able to judge how tired we are. And even if we are sleep deprived by one or two hours we sort of get by. But we've all experienced after that really fantastic holiday, where we feel like a different person...

RAZ: Yeah.

FOSTER: ...And we forget so quickly - once you get back to work and you are sleep deprived again, you forget that glorious feeling of what a good night of sleep can do to you.

So most of us of course ask the question, what do you do? Make your bedroom a haven for sleep. The first critical thing is make it as dark as you possibly can, and also make it slightly cool.

(SOUNDBITE OF TED TALK)

(SOUNDBITE OF TED TALK)

RAZ: OK, so you've probably heard this advice before - sleep in a cool, dark bedroom, no caffeine late in the day, no screens before bedtime, get on a regular schedule. But so many of us, even though we'll spend 36 percent of our lives asleep, we just don't do these things. We don't treat sleep as a need - on par with food or water or shelter.

FOSTER: Yes, yes, it is that important. And I suppose if you think about it, you know, it's 36 percent of our biology. And if we don't do it, then, you know, that amount of time is telling us that sleep of course is incredibly important. We wouldn't do it unless it was essential. Evolution doesn't work like that. It essentially the fact that we sleep so long indicates that this is a massively important part of our overall biology, and we must not ignore it. And if we do, it's at our own peril.

RAZ: Yeah, but, I mean, but what explains it? I mean, why do we ignore it?

FOSTER: I think it's in the 20th century, in particular, where we've relegated sleep as this sort of illness that requires a cure, so people during the 80s, 90s, and, you know, even very recently have sort of boasted about, oh, I did an all-nighter, you know. I haven't slept or only slept one or two hours. But in the preindustrial era, poets and society in general embraced sleep. Shakespeare is absolutely littered with quotes about sleep - the honey-heavy dew of slumber. You know, sleep, sleep, nature's soft nurse. Why hast thou forsaken me? And all of this sort of intuitive love of sleep has been lost. And science, ironically, because it's uncovering the importance of sleep, is restoring sleep in our priorities. It's something that we can't marginalize but something we must embrace once again.

RAZ: Russell Foster's entire talk can be found at ted.npr.org. More ideas about Maslow's hierarchy of human needs in just a moment. I'm Guy Raz, and this is the TED Radio Hour from NPR. Transcript provided by NPR, Copyright NPR.