This is Hidden Brain, I'm Shakir Vedantam. Last week on the show, we featured the story of Randy Gardner, a San Diego man who went 11 days without sleeping, breaking a world record. You don't need sleep. That was the thinking back in the 60s, and that's the thinking that I had.
Of course, as it turns out, that was absolutely wrong. Randy's exploit would come back to haunt him later on in life in the form of crippling insomnia. This week on the show, we continue to look at sleep and explore one of the greatest mysteries in human behavior. Nature has endowed us with an amazing brain.
So why in the world would nature have that very same brain put itself to sleep for one-third of our lives? If we didn't need eight hours of sleep and we could survive on six, mother nature would have done away with 25% of our sleep time millions of years ago. Because when you think about it, sleep is an idiotic thing to do. If sleep does not provide a remarkable set of benefits, then it's the biggest mistake the evolutionary process has ever made.
Matthew Walker is a professor of neuroscience and psychology at the University of California at Berkeley. He studies sleep and he's the author of the book, Why We Sleep. I started our conversation by asking him to tell me a story he describes in this book. It's about a pianist who relied on sleep for his creative process.
Yeah, I was giving a public lecture on sleep, and at the time we didn't know too much about sleep's role in learning and memory, of which we now know a great deal. And this wonderful, sort of distinguished-looking gentleman with a fantastic, kindly face walked to me, dressed in this great tweed suit. And he said, I'm a pianist, and I was fascinated by what you were saying about sleep and how active a brain state it is. And I wanted to tell you that there are times when I will be trying to learn a new piece, and I just can't get it.
I get frustrated, I make the same mistake at the same place every time. And I'll sometimes play late into the evening, and I will walk away, continuing to be frustrated. Have a night of sleep. And then when I come back and I sit down the next morning, I can just play perfectly.
And what he was suggesting, perhaps, was that it wasn't practice that made perfect. It was practice with a night of sleep that made perfect. I want to run two other examples by you, both of which seem to suggest that remarkable things happen to us while we're sleeping. I understand the guitarist Keith Richards from Rolling Stones kept his instrument and a recorder by his bed, and he did it in case inspiration struck while he was asleep.
Did it ever happen? It did, and it's, I think, one of the wonderful stories of sleep-inspired creativity, of which there are many. He would have this tape recorder, and he'd have his guitar, and who knows what else around in the bedroom at the time. And one morning, he woke up, and the tape had recorded all the way to the end.
And he didn't remember anything about that night. So he rewound the tape, and he played it, and he says, and this is in his autobiography, there was almost this sort of ghostly vision of him strumming the chords to satisfaction. It was a dream-inspired musical piece of creativity, followed by about 42 minutes of snoring. Lots of scientific discoveries, though, to have been birthed by way of dream-sleep-inspired creativity.
Speaking of scientific discoveries, I understand there's a connection between sleep and the discovery of the periodic table. Dmitry Mendeleev was trying to understand how all of the known elements in the universe fit together, and it was his obsession for years. And he struggled, and he couldn't figure it out. He would create playing cards with all of the different elements, and he would deal them to see if he could find some equation by way of which they all fit together.
And apparently, so the story goes, February 17th, 1869, he fell asleep, exhausted, frustrated, couldn't figure it out. And there, in his sleeping brain, emerged the solution that his waking brain could not divine. He started to realize how all of these swirling elemental ingredients could actually snap together in this sort of what he described as a divine grid, where you had each row, each period, and each column, each group, having this logical progression of atomic and orbiting electron characteristics. And he woke up, and he...
penned down this remarkable table, the table that we now call the periodic table of elements. And he noted that he made just perhaps one or two changes. And that document still exists. You can still see that dream-inspired piece of creativity.
So there is one of the greatest, I think, arguable problems to solve. And it wasn't a waking brain that solved it. It was a sleeping and a dreaming brain that did. Matthew says there are two types of sleep.
Rapid eye movement sleep, also known as REM. This is when we dream. Then there's non-rapid eye movement sleep, or non-REM. And those two types of sleep actually play out in this wonderful battle for brain domination throughout the night.
And that cerebral war is won and lost every 90 minutes, and then replayed every 90 minutes, to produce what we call a sleep cycle. And you go down into non-REM sleep first, and then you go up into REM sleep, and then you repeat the cycle. You say that non-REM sleep might be implicated or involved in cementing memories, and that there's a popular song that might get at this idea. Hello, darkness, my old friend.
I've come to talk with you again. Because a vision softly creeping left its seeds while I was sleeping. And a vision that was planted in my brain still remains. So, Matthew, what does Simon Garfunkel get right about non-REM sleep?
It is prophetic wisdom of the most remarkable kind. You know, I think that they were suggesting things there that were 20, 30 years ahead of their time. We now know that we imprint information during the day. We sort of, that seed is planted there within the brain during the day.
In other words, we learn information. But we also know that that vision that was planted in the brain still remains in the sound of silence, in the dark of night. And it's there that specifically deep non-REM sleep goes to perform its memory functions. Deep non-REM sleep almost hits the save button on those recently acquired informational pieces, so that when you wake up the next morning, you have remembering rather than forgetting.
Non-REM is all about helping us retain information. And as we start from the music of the Rolling Stones and the creation of the periodic table, REM sleep, dream sleep, spurs creativity. But Matthew says dreams also have another function. The second function, however, is very different.
That function seems to be about emotional therapy or what I would describe as overnight therapy. Dream sleep provides a fascinating neurochemical soothing balm. It is during dream sleep, and only during dream sleep, when our brain shuts off a stress-related neurochemical called noradrenaline. Now, it's a cystochemical everyone will be familiar with in the body.
That's called adrenaline. But the version of it upstairs in the brain is called noradrenaline. And it's during dream sleep but what we also know is that the emotional and memory centers of the brain during dream sleep light up in terms of their activity. And so we propose that dream sleep provides this perfect opportunity where we can start to reactivate and replay painful, difficult emotional experiences.
But we do so in a neurochemically quote-unquote safe environment. And we now understand that dream sleep actually helps separate and strip away that painful emotional sting from those informational experiences so that you wake up feeling better about it. You wake up with a memory of an emotional event, but is no longer emotional itself. It's that form of nocturnal therapy.
But what about bad dreams? Hi, I'm Greta Pittenger. Greta is a researcher at NPR and about eight or nine years ago her relationship with sleep changed. I let her tell you the story.
I had been dating a guy who is now my husband but it's time we were just dating. He rode a motorcycle and it was his only form of transportation so whenever I'd go out with him or he'd drive me to work or something I would ride on the back and have my own helmet and stuff. Late one night we were coming home from a party and we were in downtown Seattle. Streets were pretty empty but we were going pretty slow coming out of a stoplight and a large white SUV ran a red light and crashed into us from the left side.
The next thing I remember is waking up on my back in like an elevated planter kind of off on the side of the sidewalk you know there's like a street on one side and then the other side has like a little kind of retaining wall with like plants and ferns and so I was kind of halfway into that it was about I'd flown off the bike and hit my right thigh on that concrete planter and broke the femur like right in half and when I woke up I was on my back with my legs kind of dangling and there was flames around me and then like that's when I think I saw my then boyfriend Joey on the sidewalk and it was like he was also injured separately but didn't have much time to think about any of those things because luckily the police station was two blocks away and so then police were the first people there and came and dragged us out the actual crash of the car had punctured the motorcycle and then there were the first sound I really remember was an explosion of the motorcycle tank blowing up which was yeah I don't trust my memories of how intense it was but it was very very scary Joey actually broke the other femur he broke his left femur from the impact of the car I broke my right femur from hitting that wall he also broke a few other bones so I stayed in hospital for maybe four days after surgery and he stayed for I want to say at least a full week maybe ten days because he had a couple surgeries I didn't sleep pretty much at all partially because of the painkillers but I think also that's when like bad dreams were starting and I couldn't stop reliving that moment of the crash I'm not sure if I had these exact dreams in the hospital but for a couple years after all of this I would just keep having dreams about things crashing into me or things running over me and then specifically that moment also when that car hit us I would keep going back to that and I remember waking up like at the start you know like when you you wake up suddenly and sometimes you can't remember why but you know you feel like you fell like you feel like you just fell into bed that feeling I like to write and I've kept a journal since I was in fourth grade I had written about it right after it happened at my mom's insistence I was staying with her and my dad at the time and it's just like I'd wake up from my nap just bawling she said like you know maybe you should just write it down and let it go kind of hoping that might help and I think it did for a little bit but then it kept coming back and I tried to avoid it when we were talking about dreams some time ago Matthew you said that one of the potential virtues of dreams is that they might allow us to relive or experience things that happen to us or things that might happen to us in a relatively safe space and as we do this we process what happened and then potentially learn from it what about nightmares though nightmares are not pleasant they can be disruptive they can actually be acute and painful and certainly in Greta's case they were disruptive to her life why would the brain be designed to have nightmares it's not clear whether the brain actually is designed to have nightmares or whether this is actually the process going awry and we think it may be the latter because when we look at patients for example who have post-traumatic stress disorder or PTSD repetitive nightmares are actually so reliable in those patients that they actually form part of the diagnostic criteria for that disorder itself so there's something strange that we've yet to fully understand about particularly emotionally intense trauma dreams what we think is happening in the case of PTSD is that that chemical that we spoke about that normally is shut off during dream sleep the chemical noradrenaline remains too high and it may be that when that chemical is too high in its concentration we can't gift ourselves that normal therapeutic benefit that REM sleep provides so that the dreams themselves become particularly emotionally strong and difficult and you don't get that resolution the next day and so the process steps and repeats and it happens time and time again and it is perhaps only when there is some degree of contextualization be it by way of medication that is now given to certain PTSD war veterans for example drugs out there that seem to help lower that chemical that stress-related chemical give them normal dream sleep and it gives them back that ability to process those events that's one way to help another is that perhaps by journaling it and going through that process of shifting the context or reformulating it in one's mind it becomes less stressful in fact this is exactly what Greta discovered herself too so about two or three years after the crash I was finally seeing a psychiatrist about the kind of lasting trauma and trying to get over that and trying to sleep and trying to help man's on me as well and we talked about those dreams and he suggested you know I like to write and so he suggested in my journal just rewriting that dream because it's a dream it's not reality and so it doesn't need to mimic reality so just change it the way I changed that dream was that instead of a car coming and hitting the motorcycle the motorcycle transformed into a winged horse and flew away away from the car away from all that crash and then just landed safely back at our apartment dropped us off and so writing about it again years later but in a totally different way not trying to be accurate not trying to remember was much different it definitely got me to stop having those vivid dreams I've had flying dreams in the past but I started to have more types of those dreams of kind of being lifted away from gravity and from the weight of these emotions you know like when you wake up from a dream and it doesn't really leave a mark on you that was a good feeling to kind of be like oh yeah I guess I did have that dream oh yeah that was nice just like this past month Joey and I bought mopeds which is like something he used to do before he even had a motorcycle and I have never ridden before and I'm like I feel like such a badass on this like little like it's such a dorky little thing it's like half bike with a tiny engine on it and it sounds like super high pitched and has the dorkiest horn but it's like yeah look how cool I am I have to wear a full face helmet when we come back we look at the amazing range of things a good night's sleep can accomplish you know sleep is the Swiss army knife of health so let's talk just for a bit about the amount of sleep that people need you and many other experts say people should strive to get eight hours of sleep every night to tell you the truth I got about six hours last night and I feel fine tell me where you live I'm coming around tonight we will have a sleep salon of sleep I will inflict change no matter what here's my question Matthew if I can get away with sleeping 25% less than the recommended amount one night why can't I do it every night and just think of the upside you know I can spend two hours every day reading wonderful books like yours building a better podcast being more productive surely it's a good thing if we didn't need eight hours of sleep and we could survive on six mother nature would have done away with 25 of our sleep time millions of years ago because when you think about it sleep is an idiotic thing to do you're not finding a mate you're not reproducing you're not finding food you're not caring for your young worse still you're vulnerable so on any one of those counts it should have been excised from the evolutionary process so as it's been said before if sleep does not provide a remarkable set of benefits then it's the biggest mistake the evolutionary process has ever made and it didn't make a spectacular blunder in putting in place through 3.6 million years of evolution this thing called an eight hour sleep need so i know that you think you're okay with six hours of sleep but trust me you're not and we know this to be true that your subjective sense of how well you're doing on insufficient sleep is a miserable predictor of objectively how you're doing with to the sleep so it's a little bit like a drunk driver at a bar picks up the keys after you know six or seven shots and says i'm fine to drive off i go and your response is no i know that you think you're fine to drive subjectively but objectively trust me you're not you're impaired it's the same case with insufficiency too i think it's one of the reasons that we often underestimate how damaging a lack of sleep is on our health and our wellness and our cognitive function you know i remember once going to a talk that showed the level of light pollution on the planet the parts of the planet where there were the highest levels of artificial light and then the researcher took that the image off the screen and replaced it with an image showing the distribution of prostate cancer around the world and there was a remarkable correlation between the areas of the world which have light pollution where presumably people are staying up later in later at night and presumably getting less sleep than they need and the incidence of prostate cancer now of course this is a correlation we don't know if one is connected to the other but you say there has been some evidence at least that sleep might be implicated in the development of cancer there is and it's fast becoming i think stronger evidence and causal as well we know for example that one single night of short sleep in these laboratory studies where you perhaps are limited to just four hours of sleep for one single night the next day that will drop critical anti-cancer fighting cells called natural killer cells by 70 percent seven zero that is an alarming state of immune deficiency and it happens quickly after essentially just one bad night of sleep we also know from the associational evidence that insufficient sleep is linked to cancer of the bowel cancer of the prostate and cancer of the breast and the link between a lack of sleep and cancer has since become so strong that the world health organization has now classified any form of nighttime shift work as a probable carcinogen in other words jobs that may induce cancer because of a disruption of your sleep weight rhythms for women that have net arbejde in many years you know that there is a risk for breastcraft in british ones in denmark based on the strength of the evidence that we were just discussing became the first country to actually pay worker compensation uh to women who had developed breast cancer after years of nighttime shift work in government-sponsored jobs there are clearly some professions where we do want to need people to work um those those shifts you know if i have a burst appendix at three o'clock in the morning i'm so grateful to people at the hospital who will see to me and save my life so i think automation is going to help i think with this revolution of technology where we can start to limit that type of shift work whenever possible we should absolutely do that and start to scale it back we can also architect professions better i think we know that people are genetically predisposed to being nighttime people or morning people so why aren't we asking those questions and seeing if the people who would much prefer what we call the owls who like to go to bed very late and wake up very late why don't you think about asking those questions and seeing if we can help people sort of fit what we call their chronotype which is their morningness or eveningness propensity fit that into their job flexibility in those workouts and see if there's some overlap i understand that before you came to Berkeley you taught at harvard and you once stirred a bit of controversy among the faculty when you wrote an op-ed for the harvard crimson what did you recommend in the op-ed well i was asked based on the findings that we were publishing regarding how important sleep is for memory um to write a piece on this and i ended up rather than describing the science actually going after the structure of education itself because what we tend to do at higher education institutes is have a long term or semester and then we end load that semester or that quarter with all of these finals where people have to cram vast amounts of information to the brain and what do they do they end up pulling the all-nighter and we've done the studies and it's very clear if you pull the all-nighter you're about 40 percent worse at cramming facts into the brain so that behavior is contrary to a sound education and i went to task and i said that in fact this was not the student's fault it was our fault educators because we are designing a system that actually co-opts and encourages that type of behavior pulling the all-nighter so if our goal as educators truly is to educate and ps not risk lives in the process then i think we were failing our students with this model of end-loading schools uh school semesters or university semesters with all of these exams when you were a kid your family took a vacation to greece and then when you visited greece again as an adult you noticed a very big change what was it back in the 1980s when i went on holiday there were signs in the shop store windows that would give the opening hours and they would open from between sort of 10 to 2 and then it said closed between 2 to 4 or 2 to 5 p.m and then open from 5 through until 10 or 11 in the evening and it was so different to the way in which sort of shops back in england would operate you know maybe there was a one-hour lunch break or for the most part it was nine to five hours classic and of course what it was describing was this classic siesta-like behavior now back in the mid-1990s uh the greek culture actually started to abandon the siesta-like practice and fortunately or unfortunately a group of scientists from harvard university school of public health decided to quantify the health consequences of this radical change in sleep practice and with many greek tragedies as was the case here the results were heartbreaking but in the most literal sense what they actually observed was a 37 percent increase risk for death from heart attacks across that six-year period as a consequence of doing away with that siesta behavior it was actually particularly strong in um in working males almost a 60 percent increased risk of death from heart attacks so i think that that again suggests not only how important sleep is and when sleep is taken away we see this type of danger to our cardiovascular health it raises actually a different question which is how should we be sleeping and are we sleeping currently the way in which we do through modernity and industrialization in the way that we were designed the answer may actually be no because the way that we currently try to sleep is what's called monophasic sleep where we sleep one single bout throughout the night we aim for however much we can um but if you look at some cultures who are untouched by electricity sort of hunter-gatherer tribes for example they actually tend to sleep biphasically they tend to sleep for sort of six seven hours at night then they'll have a siesta like nap in the afternoon and it turns out that we all have this in us it is genetically hardwired that we all have a pre-programmed drop in our alertness sometime after lunch now many of us think it has to do with the lunch that we have it's actually not you can stop the lunch and you still get it it's sort of you know you've seen those boardroom meetings you know in the afternoons where you get lots of that head nodding that stops to happen you know it's not people listening to good music um it's actually people giving way to this this hardwired programmed drop in our alertness which actually does argue from an evolutionary perspective that we should be sleeping biphasically rather than monophasically two bouts of sleep rather than one perhaps i have to say matthew that in some ways when it comes to sleep there's almost a sense of people bragging about not getting enough sleep i mean certainly in the united states it's seen as a badge of honor to say you know i get very little sleep because i'm so productive and i work so hard and i achieve so much oh you're so you're so right because what we've done is actually stigmatized sleep sleep has an image problem right now it's not just in america you know and we do we label people who get sufficient sleep and i choose that word very carefully with being lazy with being slothful and that is a terrible disservice to society and we don't always have that opinion by the way you know no one looks at an infant sleeping during the day and says what a lazy baby and we don't you know we laugh but we don't because we know that sleep at that time of life is non-negotiable it's absolutely necessary but now even into early childhood not only do we abandon the notion that sleep is important and should be celebrated we chastise people for getting sufficient sleep and give them this this label tell me about your non-sleep habits and tell me what you do to ensure you get a good night's rest i'm going to sound like a desperate prude and i'm so sorry it sounds hokey as well but i actually give myself a non-negotiable eight-hour sleep opportunity every night if you knew the evidence as i do you would trust me you wouldn't do anything different you know sleep is the swiss army knife of health you know when sleep is deficient there is sickness and disease and when sleep is abundant there is vitality and health my family for example has a history of cardiovascular disease sleep is a wonderful form of nighttime blood pressure medication why would i skip on it why would i try to give way to the genes that i've been given in this genetic lottery and succumb to cardiovascular disease so i have to say i'm i'm sorry i do practice what i preach do you try and stick to very rigid hours when sleeping at the same time waking up at the same time do you use an alarm clock do you avoid technology before you go to sleep i do so i stop checking my email at a certain time i have software installed on my computers that does away with a harmful blue light and i shut them off at least an hour and a half before bed but you mentioned perhaps the single most important sleep prescription that i could give everyone which is regularity just go to bed at the same time wake up at the same time no matter what whether it's the weekday or the weekend if you've had a good night of sleep or a bad night of sleep stay as regular as you can that's the best piece of advice i can give you for getting good sleep at night matthew walker is a professor of neuroscience and psychology at the university of california in oakley he studies sleep and he's the author of the book why we sleep matthew thank you for joining me today on hidden brain you're very welcome thank you very much and i do hope you sleep well tonight this episode of hidden brain was produced by paf shah our team includes tara boyle jenny schmidt maggie penman renee clarr and reyna cohen our unsung hero this week is holly hersfeld holly is an intern at npr and like many of the multi-talented interns who come to us holly happens to have a special skill she plays the piano when we wanted someone to play a piano riff for us at the start of this episode we turn to her thanks so much holly for more hidden brain you can follow us on facebook twitter and instagram and listen to my stories on your local public radio station if you haven't subscribed to the podcast please do and if you've never told a friend about hidden brain try it and see how much more they love you i'm shankar ve dunton and this is npr i hope you have sweet dreams you