Last night I attended Matt Walker’s conversation with Indre Viskontas as part of the City Arts & Lectures series at the Nourse Theater on the science of sleep. He and Indre did an excellent job of conveying a ton of useful information in a conversational format that was both accessible and entertaining. Some highlights from the talk:
1. Sleep is so important from an evolutionary standpoint that organisms will develop byzantine mechanisms to make sure they get their shut-eye without becoming dinner. For example, marine animals (e.g. dolphins) sleep with one brain hemisphere at a time. And when a flock of birds sit on a branch, the birds in the middle will go to sleep with both hemispheres. The birds on the sides, however, will sleep with only one hemisphere and keep one eye open as a lookout – the opposite eye from the birds on the other end. Then, after a while, they will turn around and switch hemispheres, close one eye and open the other! That way, they always have a 360-degree lookout for predators. This is a movie I would pay to watch.
2. Every language that Walker has looked into has an expression for “sleeping on the problem” as a prescription for breaking through a mental impasse. None of those languages has an expression for “staying awake on the problem.” All these cultures have noted an integrative, problem-solving aspect to sleep, which scientists are just beginning to understand.
Also worth noting is that the French expression is to “sleep with the problem.” But of course.
3. Thomas Edison was well aware of the creative power of sleep – or more accurately, that groggy state of half-sleeping, half-waking called the hypnagogic state. So when he had a tough problem to solve, he would go for a nap in a leather chair with a pair of steel balls in his hand and a metal tray underneath. As he got groggier, his muscle tone would relax until his hand released the balls into the tray, waking him with a clang. He would then return to work with the creative solution just presented to him.
4. One of the most dramatic pieces of data on the effects of sleep deprivation comes to us from daylight savings time. The day after clocks are turned forward an hour and everyone gets one less hour of sleep, there is a sharp spike in heart attacks and auto accidents. The after the clocks are turned back and everyone gets an extra hour of sleep, there is a noticeable dip in heart attacks and auto accidents. This kind of clear-cut public health evidence is really hard to come by, and it’s a surprise that governments haven’t acted on it.
5. In light of the strong evidence that kids and adolescents need more sleep than adults – especially when they tend to stay up late – it’s almost criminal that schools start at 8am, and sometimes as early as 7.30am. One study followed the honor students at a school where the top 1% of the class had an average SAT score of 1288 when the schoolday started at 7.30am. When they switched the start time to 8.30am, one year later, that average SAT score for those same students had shot up to 1500. By that token, the hidden cost of reduced learning and memory for our kids must be enormous.
6. The older you get, the less slow-wave deep sleep you get. Slow-wave deep sleep is closely associated with learning and memory, and this seems to be one of the inevitable consequences of aging. It may be possible to enhance slow-wave deep sleep through transcranial direct current stimulation (tDCS), but this development is in its early phases.
7. Two things that really aren’t good for your sleep are the most common drugs consumed by mankind: alcohol and caffeine. Alcohol acts as a sedative, which obliterates your restorative rapid-eye movement (REM) sleep. Caffeine, on the other hand, blocks adenosine, the brain’s own sleep-inducing agent. As a result, your brain thinks “oh, no adenosine around, I should keep going” even as your body’s metabolism is slowing down and getting ready for a super-extended nap. Once the effects of caffeine wear off, now you have an excess of adenosine floating around, which causes you to be extra-drowsy – the “caffeine crash” familiar to coffee drinkers (of which I know nothing, since I don’t touch the stuff).
Also, sedatives in general are bad for sleep. You’re knocked out, but it’s not the right quality sleep.
8. Our tendency to be a morning person (“larks”) vs late-night (“owl”) is determined genetically. Unfortunately, society is structured to put owls at a disadvantage. Walker’s explanation of why larks and owls exist is fascinating and eminently plausible. When studying the sleep habits of pre-industrial societies with no electricity – e.g. the !Kung-san and Hadza – we find that they also have larks and owls. So one guy goes to bed at 8pm and gets up at 4am; another goes to bed at midnight and wakes at 8am. Now if all of the tribe were synchronized in their sleep, they would be vulnerable to predator and invader attack for 8 hours. Now, with a diversity of chronotypes, that risk is 4 hours – cut in half. Evolution will strongly favor an adaptation that results in a 50% improvement in survival.
9. 90 million people in the US are suffering from some kind of sleep deprivation, which wreaks particular havoc on the endocrine system. If you sleep for 5 hours for three consecutive nights, your lab tests will show that you’re now borderline diabetic. It’s that fast, and that bad.
Also, you never fully get back the sleep you lose. College kids who are “bulimic” with their sleep – purging during the week as they stay up late, and binging over the weekend as the sleep in – are developing a very bad habit that they’re likely to carry into adulthood.
10. During the question and answer session, Walker baited the audience with a coy “I usually get a question about dream interpretation.” One audience member bit, describing his dream of a box of jello that changed color when his sister was round or somesuch. Walker paused pensively, then said, “I think this means that you feel you don’t have enough time.” After getting a surprised “Oh!” from the questioner and nods of approbation from the rest of the audience, Walker said, “Now, I have to apologize, because I’ve been a little bit disingenuous here. Because that’s the interpretation I give to every dream I’m told about in these kinds of talks. And if you were to ask five psychotherapists to interpret a dream for you, they would give you five different answers. It’s just not scientific, and I apologize for the trick but I hope you see the bigger point.”
11. Some principles of basic sleep hygiene:
- Sleep in a cool room, ideally 65-68ºF (18-20ºC). The slowing down of the body’s metabolism is its signal to go to bed. A cool room helps that. Paradoxically, this is also how a hot bath before bed works. The hot water dilates your peripheral blood vessels. When you step out of the bath, you then lose more body heat than normal. This cooling of the body aids sleep.
- Make it dark!
- Go to bed and rise at the same time every day.
- No alcohol or caffeine close to bedtime.
- Electronic devices such as cell phones and iPads send blue light to your brain, which makes it think that it’s still daytime. This delays sleep onset.
Two personal notes:
- I’m in the process of researching a book, part of which covers the importance of sleep to our long-term well-being. If you have good resources (e.g. a definitive recent book), please send them my way.
- Just for kicks, I chose not to take any notes during this talk and used mnemonic techniques instead. So everything in this article I wrote from memory (after sleeping on it, of course). Any gross exaggerations and pure fabrications you can blame on that :) The technique I used is fairly straightforward, so if you’d like to learn how, let me know! If there’s enough demand, I may even create a course around it.