Would you like to be smarter? Have a better memory, more easily understand human emotion, and earn more money? Would you like to be more attractive? Lose weight while having more people think you are desirable? Would you like to be healthier? Substantially decrease your risk of cancer, heart attack, diabetes, and general disease?
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If all those questions did not immediately move this email to your spam folder, all those answers can be yours - and more! But it’s no easy fix. It’s going to involve a commitment of perhaps nine hours of your day. Everyday.
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I was once a history major at Stanford, an engineering school that requires all undergrads to take a science course. This subject not being my comparative advantage, I did what all humanities students should do: ask the football team how they filled the requirement. The “Sleep” class they suggested changed my life and the subject can change yours. I used to be of the mindset that every hour sleeping was an hour unavailable for other activities. Now I know better.
Why We Sleep is a book that summarizes the latest best research on how you should spend a third of your life. Sleep is an evolutionary mystery - why would we enter a daily ritual of “apparent coma… often filled with stunning, bizarre hallucinations” when we could be out gathering food, reproducing, or protecting our tribe? There must be some point.
In fact, there are a lot of points.
Figure 3. The evolutionary “ascent of man” is not as dramatic when depicting the monkey, neanderthal, and human asleep. Especially since monkeys technically sleep in trees, so we’ve actually descended.
Sleep is crucial to your immune system. To use just the two leading causes of death in America, sleeping less than seven hours a night more than doubles your risk of cancer and more than quintuples your risk of cardiac arrest. In fact, during the annual spring forward switch to daylight savings time, there’s a substantial spike in heart attacks during that single morning.
Sleep decreases your hunger, improves your exercise, and makes you look better. The sleep-deprived are significantly hungrier and, in particular, have up to 40% more cravings for unhealthy foods. When trying to burn calories, less sleep is correlated with decreased exercise intensity and duration the following day - as well as greater chance of injury. No wonder the U.S. Olympic team and professional sports teams now have sleep consultants!
But let’s talk sex appeal. One researcher took a group of young people and photographed them under identical conditions on two different days - same time, same indoor lighting, same grooming etc - except on day one, the subjects had a full eight hours of sleep and on day two, the subjects were permitted less than six hours of sleep. Independent judges, unaware of the difference, overwhelmingly considered those who got their beauty sleep more attractive. And for the macho who pride themselves on not needing sleep, “Men who report sleeping too little—or having poor-quality sleep—have a 29 percent lower sperm count than those obtaining a full and restful night of sleep, and the sperm themselves have more deformities...these under-slept men also have significantly smaller testicles than well-rested counterparts.”
Figure 4. The optimal strategy for sleeping with someone might actually be sleep.
Sleep powerfully affects your memory, your creativity, your ability to control your own emotions and read others’. But different stages of sleep affect different things: “When it comes to information processing, think of the wake state principally as reception (experiencing and constantly learning the world around you), NREM sleep as reflection (storing and strengthening those raw ingredients of new facts and skills), and REM sleep as integration (interconnecting these raw ingredients with each other, with all past experiences, and, in doing so, building an ever more accurate model of how the world works, including innovative insights and problem-solving abilities).” What’s crucial to understand is that REM sleep tends to occur at the end of a typical human sleep cycle - so if you sleep 6 hours instead of 8, you are getting 25% less sleep overall but 60 to 90% less REM sleep.
Figure 5. Without REM, it’s the end of the world as we know it. Everybody hurts sometime but it’s much better to #9 dream. Granted, at this point, you probably want 60-90% less REM.
We only have so much gas per day: “After sixteen hours of being awake, the brain begins to fail. Humans need more than seven hours of sleep each night to maintain cognitive performance. After ten days of just seven hours of sleep, the brain is as dysfunctional as it would be after going without sleep for twenty-four hours. Three full nights of recovery sleep (i.e., more nights than a weekend) are insufficient to restore performance back to normal levels after a week of short sleeping.” The less you sleep the night after learning something, the more unlikely you are to recall it. But even just less sleep over time can mean a 40% reduction in your memory. So make sure to get at least 8 hours of sleep after reading this newsletter!
One of the biggest problems, however, is that the sleep-deprived have no idea how impaired they are and “consistently underestimate[] their degree of performance disability… It is the equivalent of someone at a bar who has had far too many drinks picking up his car keys and confidently telling you, ‘I’m fine to drive home.’” That analogy is particularly adept because “vehicular accidents caused by drowsy driving exceed those caused by alcohol and drugs combined” and, in fact, drowsy driving can be worse because “drunk drivers are often late in braking, and late in making evasive maneuvers. But when you fall asleep, or have a microsleep, you stop reacting altogether.” There are striking studies within the book about sleep-deprived people doing simple tests indicating, for example, whether they heard a sound, and missing things altogether every few minutes - compared to when they are adequately-rested and missing zero.
Powerful evidence of the positive effect of sleep comes from standardized testing. Why We Sleep explains how teenagers are on a different circadian rhythm than their parents and feel biologically compelled to go to bed later. Asking your teen “to wake up at seven the next morning and function with intellect, grace, and good mood is the equivalent of asking you, their parent, to do the same at four.” Schools in Edina, Minnesota changed their start time from 7:25 AM to 8:30 AM and students reported getting an average of 43 extra minutes of sleep a day. The following year, average verbal SAT scores for the top performing students shot from 605 to 761 and, in math, from 683 to 739. You may never need to take another standardized test again but know also that sleep is apparently correlated with higher income!
Figure 6. Turns out, whether it’s the Sleep Aptitude Test or life, hitting the sack may be better than hitting the books. You $nooze you win.
Are you getting enough sleep? Probably not. Most Americans don’t. My Stanford professor, the sleep pioneer William Dement, used to say that if you lay down for 10 minutes in the middle of the day in a dark cool room and fell asleep, you needed more sleep at night. Why We Sleep suggests that if you could go back to sleep at 10 AM, if you need caffeine before noon, or if you would substantially oversleep your alarm clock - all are signs you need more sleep. And don’t confuse actual sleep with the opportunity you give yourself to sleep. If you go to bed at 12 and have an alarm for 8, you’re not actually sleeping 8 hours. Only teenagers enjoy 95%+ sleep efficiency. You may need to be in bed 9 hours.
Figure 7. Why We Sleep also suggests that if you find yourself re-reading sentences for their meaning, you may not be getting enough sleep. Or I just have atrocious handwriting.
So what are best practices?
Have a consistent sleep schedule. That means going to bed and waking up the same times everyday, including weekends. I personally have an alarm clock every night reminding me that bedtime is imminent. Relax and try not to stress out before you go to bed. Don’t nap after 3 PM because it could affect your ability to sleep. If you initially can’t sleep, don’t lie awake. Go do something boring and return when you get drowsy. And in the morning, do something active - shower, exercise, talk to somebody - to jolt yourself awake. Ideally avoid an alarm to wake up and do your best to avoid the snooze button - it puts a lot of repeat stress on your heart.
Sleep in a dark, cold, quiet room you associate exclusively with sleep.
Imagine your ancestors seeking out a cave. Your body is on a circadian rhythm a little longer than 24 hours and your brain uses sunlight to try to keep it in check. The problem is that artificial light, especially from your television, computer, and phone, tricks your brain into thinking it’s still the day. Biologically, you should feel like going to bed between 8 and 10 PM but modern light pushes that impulse 2-3 hours. Ideally, you’d avoid screens altogether before bed and get around by dim lamps. But you can mitigate modernity by using Night Shift on your phone and Flux on your computer to turn down the most harmful blue light - unless you are editing colors, you should experience no productivity loss. When I watch a movie at night, I use blue-light blocking glasses. And in your bedroom, you need blackout curtains or a sleep mask to block out any outside light. Know that light does enter your brain through your closed eyelids!
Figure 8. The ideal sleep conditions. And, simultaneously, perhaps the best example of my drawing skills.
Darkness and quiet are kind of obvious, though not necessarily practiced at the ideal extremes - what about temperature and the thermostat wars that families routinely wage? The science says that “to successfully initiate sleep… your core temperature needs to decrease by 2 to 3 degrees Fahrenheit…. A bedroom temperature of around 65 degrees Fahrenheit (18.3°C) is ideal for the sleep of most people.” Brrrr…...
Building on the previous point about not staying awake, your brain should associate your bed with sleep. Your bedroom should be as spare as possible - remove anything that might draw your interest, especially clockfaces. Teach yourself that your bed is for sleep and you shouldn’t have any trouble in the future.
The closer you get to sleep, avoid alcohol, caffeine, and exercise.
Alcohol has two really bad impacts: first, it “litter[s] the night with brief awakenings. Alcohol-infused sleep is therefore not continuous and, as a result, not restorative… Second, alcohol is one of the most powerful suppressors of REM sleep that we know of.” In one study, three groups of students were exposed to the same complex new material. Teetotaling students had as much retention a week later as they did the day of learning. Students who got drunk the night of learning the material had 50% retention. And amazingly, those who got drunk after two nights of full sleep after learning the material only had 60% retention. But don’t think that you have to be drunk to reduce your sleep quality - Why We Sleep actually encourages day drinking so all alcohol is out of your system by the time you go to sleep. Or you can join me among the teetotalers.
Caffeine has a different bad effect. Your body has two main inputs for your sleep. The first, your 24+ hour circadian rhythm, has already been discussed. “The second factor is a chemical substance that builds up in your brain and creates a ‘sleep pressure.’” Caffeine relieves that sleep pressure temporarily but is the equivalent of plugging your ears with your fingers to avoid sound - except that sound piles up and when you remove your fingers, you get at once all the sound you were missing. Hence the classic caffeine energy crash. The drug has an average half-life of five to eight hours - meaning 50% of the caffeine you consume could still be in your system eight hours after you consume it. And bear in mind: caffeine isn’t limited to coffee and soda - it’s in your chocolate and even “decaffeinated” coffee that “usually contains 15 to 30 percent of the dose of a regular cup of coffee.”
While we’re discussing drugs, we should note that Why We Sleep advises very strongly against sleeping pills. They fail to produce anything near the quality of natural sleep, have a variety of side effects, encourage dangerous dependency, and the over-the-counter versions often substantially lie about their promised dosages.
Otherwise, exercise is an encouraged activity but it increases your core body temperature for up to two hours afterwards and should therefore be avoided in the lead up to bed.
For more insight and best practices, check out Why We Sleep. Some other interesting things you’ll discover: how owls and larks likely developed to ensure tribes were safe the maximum amount of time; how you can only adjust one hour every day as you move time zones; how all humans, regardless of culture or location, have a genetically determined dip in alertness in the mid-afternoon; and how the crazy hours young doctors work were designed by a coke addict. As a result, always ask your doctor before your (hopefully not mid-afternoon) surgery: “How much sleep have you had in the past 24 hours?”
Figure 9. Click here to buy Why We Sleep. 9/10. The best recent book about how and why you should rethink a third of your life. All the more important if you’re following the recent advice of other newsletters suggesting you have lots of kids.