Matthew Walker: Why Is It Essential To Make Time For Sleep? Sleep is crucial for our health — and there are alarming consequences when we don't get enough. Matthew Walker explores the many benefits of a full night of sleep, and how to make sleep a priority.

Matthew Walker: Why Is It Essential To Make Time For Sleep?

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript


It's the TED Radio Hour from NPR. I'm Manoush Zomorodi. And today on the show, we're giving in to things that take time, like sleep.

MATT WALKER: There is no rushing sleep. One of the unusual things relative to diet or exercise is that you get to decide, do I exercise and for how long? Do I rush it? Do I not rush it? With sleep, you don't have a choice.

ZOMORODI: This is Matt Walker.

WALKER: I am a professor of neuroscience and psychology at the University of California, Berkeley, and I'm also the director of the Center for Human Sleep Science here at UC Berkeley.

ZOMORODI: And Matt says optimizing how your brain works when you sleep - it's not really possible.

WALKER: You can't just generate sleep, you know, consciously and say, OK, tonight off the menu, I'm going to actually dial up my deep sleep by an hour and a half. I think I'm going to reduce my REM sleep down maybe a little bit. I'll bring it back down to maybe just 50 minutes tonight. You can't do that. You have to let sleep unfold naturally. You have to give in to sleep and give sleep time to do all of the wonderful things that we know it does. Your brain is erupting in these incredible bursts of electrical activity going through all of these fantastic sleep stages. It's an electrical ballet that takes place at night.

ZOMORODI: That electrical ballet of sleep is crucial for every aspect of our health. And when we don't make time for sleep, there are consequences.

WALKER: Once you drop below seven hours, we can start to measure objective impairments in your brain and your body. The shorter your sleep, the shorter your life. Short sleep predicts all-cause mortality.

ZOMORODI: We humans have evolved to need a specific amount of sleep.

WALKER: It's taken Mother Nature, let's say, 3.6 million years to put this essential need of seven to nine hours in place for the average adult. And for us to think, perhaps with a little bit of hubris, that we could come along and start to say, you know, I can train myself to survive on, let's say, just six hours or 6 1/2 hours a night...


WALKER: ...It's a dangerous thing. You know, when you fight biology, you normally lose. And when you lose, the way that it's usually revealed is disease and sickness. And unfortunately, that's what we see with insufficient sleep.


ZOMORODI: So to understand the strength of a full night's sleep, we need to understand what's happening in our brains, especially during those last few hours before the alarm goes off.

WALKER: When you fall asleep tonight, you're going to experience two main types of sleep.

ZOMORODI: You may have heard of these before. There's rapid eye movement or REM sleep and non-REM sleep. And our brains and bodies need to cycle through both.

WALKER: Approximately every 90 minutes, you go through a cycle of non-REM to REM. But what changes, however, is the ratio of non-REM to REM within those 90-minute cycles as you move across the night such that in the first half of the night, the majority of those 90-minute cycles are comprised of lots of deep sleep and very little REM sleep. But as you push through to the second half of the night, that seesaw balance actually shifts. And now you have much more rapid eye movement sleep.

ZOMORODI: I mean, that is fascinating. So you can't hack this. You can't say, well, I got four or five hours of sleep. That's good enough. Like, what happens when we do skimp on sleep? Because, I mean, we all do it.

WALKER: So let's say that, normally, you would sleep eight hours, but today, you want to get a jump start, and you've got an early morning meeting, or you want to get to the gym. And so instead of going to bed, let's say, at 10 p.m. and waking up at 6 a.m., you're going to wake up at 4 a.m.


WALKER: How much sleep have you lost? Well, you've taken away two hours from your eight-hour night of sleep, so you've lost 25% of your sleep. Well, yes and no. You've lost 25% of your total sleep, but you may have lost 60, 70, 80% of all of your REM sleep because that's when you're getting your REM sleep in those last morning hours. So there are ramifications there. So what do those things do for our brain and our body?

Well, firstly, what we know is that it's during deep sleep at night that your memory systems undergo a radical change. The first thing that we've learned is that you need sleep before learning to actually prepare your brain, almost like a sort of a dry sponge, ready to initially soak up new memories and lay down those sort of - those new memory traces in the brain.


WALKER: But we've also learned that you need sleep after learning to then take those freshly minted memories in the brain and cement them and solidify them into the neural architecture of the brain.

ZOMORODI: Matt Walker picks up this idea from the TED stage.


WALKER: 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. 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.

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. Sleep will take those new memories, and it will start to integrate them and associate them with all of your past back catalog of autobiographical memories. So in other words, you wake up the next morning with a revised mind-wide web of associations, and it's sort of like group therapy for memories.

ZOMORODI: (Laughter).

WALKER: You know, at the end of the day, everyone gets a name badge, and then sleep gathers in all of this information. And I would argue that during deep sleep, that's taking memories and sort of improving them and strengthening them. But what dream sleep does by interconnecting them is it shifts us from knowledge, which is the individual facts, to wisdom, which is knowing what it all means when you fit it together. And I think it's probably no coincidence that you've never been told to stay awake on a problem.

ZOMORODI: You know, actually, you're making me think of the saying, never go to bed angry with your partner. And actually, I have found that once I - it's better to go to bed angry 'cause then you don't have an argument 'cause when I wake up in the morning, I feel like I have a new perspective on the issue. It sounds like maybe I actually do. Maybe my brain's been working out the problem overnight.

WALKER: Well, it's been working out the problem. But this brings us on to another benefit of sleep for the brain, which is that sleep provides a form of emotional first aid. Sleep provides overnight therapy. And what we've discovered is that sleep will take these difficult, painful experiences, sometimes even moving into the area of trauma. And it will act almost like a nocturnal soothing balm. And it will just take the sharp edges off those emotional memories so that when you come back the next day, they don't feel as emotional anymore. So, yes, you remember what happened yesterday, but it - you no longer regurgitate that same visceral, emotional reaction that you had at the time of the event.

ZOMORODI: My saying to my kids is, sleep makes everything better.

WALKER: Yeah. There is no major physiological system of the body or major operation of the brain that isn't wonderfully enhanced by sleep when we get it or demonstrably impaired when we don't get enough.


WALKER: At this point, you may be thinking, oh, my goodness, how do I start to get better sleep? What are your 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.

The second is keep it cool. Your body needs to drop its core temperature by about 2 to 3 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.

Sleep, unfortunately, is not an optional lifestyle luxury. Sleep is a non-negotiable biological necessity. It is your life support system, and it is Mother Nature's best effort yet at immortality. 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. And with that, I will simply say good night, good luck, and above all, I do hope you sleep well. Thank you very much indeed.


ZOMORODI: That's Matthew Walker. He's a sleep scientist and the author of the book "Why We Sleep." You can see his full talk at

Copyright © 2021 NPR. All rights reserved. Visit our website terms of use and permissions pages at for further information.

NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.