“That we are not much sicker and much madder than we are is due exclusively to that most blessed and blessing of all natural graces, sleep,” the British writer Aldous Huxley once observed.
Huxley, who died in 1963, had no idea what temptations would get in the way of our sleep in the digital age. About 35% of American adults get less than seven hours of sleep a night, according to the Centers for Disease Control (CDC), which isn’t enough. Often we either can’t get to sleep, or we think of sleep as wasted time. What actually goes on while we’re lying there? Why are we designed to do nothing for a third of our lifetimes?
The answer is that our bodies are doing necessary work to keep us going when we’re awake. Scientists still have plenty to learn about how, but what we do know is absolutely fascinating. From academic studies to cultural practices, these 12 interesting facts certainly won’t put you to sleep.
Night owls have a reputation for being lazy, but many of them might just have drastically different internal clocks than early birds and others. We all have a biological timer called a circadian rhythm that controls, among other things, when we feel awake and when we feel sleepy. It can change at different points in our lives, too.
While the vast majority of people are somewhere in the middle, around 30% of people are early-morning or late-night people. It’s not that early birds are more productive or that night owls are lazy; they’re just literally on a different biological schedule. Trying to force either one to conform to a standard human schedule could even have health consequences as a result of chronic sleepiness — although your boss might not accept that as an excuse for coming in late.
It’s normal for pregnant people to feel punches and kicks as the fetus growing inside them grows bigger, but what are babies doing when they’re not kickboxing? Because growing brains and bodies is hard work, the vast majority of their time — up to 95% of it, even close to term — is spent sleeping.
Babies tend to sleep a lot during the day and be most active in the evening, disturbing plenty of expectant parents just as they’re trying to go to sleep themselves. This could be due to their unique circadian rhythms, or because movement during the day lulls them to sleep. Newborns sleep between 14 and 17 of every 24 hours, although rarely more than a few hours in a row.
Snoring happens when something blocks or narrows an airway while you’re sleeping, causing vibrations in your throat muscles. Sometimes it’s caused by a sinus infection, a polyp, a cold, or sleep position. It can be relatively benign, but it could also be a sign of obstructive sleep apnea, a condition where people stop breathing periodically while asleep. This type of apnea is caused by the muscles in the back of the throat relaxing so much that they block your airway. Let your doctor know if you snore, especially if you’re usually sleepy during the day.
Sleep patterns can change for many different reasons, including age, hormones, and work shifts — and it turns out your bedtime Wordle ritual might be a factor, too. Smartphones give off blue light, which, in nature, is more prevalent in the morning. This can keep your brain from producing enough melatonin, a hormone that helps with sleep, which then disrupts your natural circadian rhythm. Other technology that gives off blue light, such as tablets and laptops, can also mess with your sleep.
Some people wear blue-light-blocking glasses to reduce the impact of smartphone use, and while they’re not harmful to wear, the evidence of their actual effectiveness is inconclusive.
While an all-nighter here and there probably isn’t the end of the world, you shouldn’t plan to operate any heavy machinery the next day. Even if you feel fine, you could have delayed reaction times, an inability to focus, and unstable moods — you know, like when you’ve had too much alcohol.
While the effects of sleep deprivation and alcohol vary from person to person, the Centers for Disease Control and others estimate that going 24 hours without any sleep is roughly the equivalent of having a blood alcohol level of 0.1%, past the legal limit for driving in the United States. So if you’re feeling a little woozy after an all-night project, try sleeping it off if you can. Naps probably can’t fix a long-term sleep-deprivation issue, but a quick snooze may restore some alertness.
In 1951, a graduate student at the University of Chicago, Eugene Aserinsky, hooked up his 8-year-old son, Armond, to a device that tracked eye movements and brain waves. After Armond fell asleep, Aserinsky noticed from another room that the eye-tracking “pens” were swinging back and forth. Thinking Armond must be awake and looking around, Aserinsky went to investigate and found the boy sleeping deeply, his eyes closed. Aserinsky’s paper, published in 1953, was the first time REM sleep had been described; before that, scientists had believed that the sleeping brain was more or less turned off.
We now know that not just humans but all land mammals and many birds undergo spells of REM, or Rapid Eye Movement, sleep. In those spells, the heart rate speeds up, breathing becomes irregular, and brain waves are more variable. Major muscles that we normally control can’t move.
REM sleep first occurs about an hour to 90 minutes after falling asleep. As we age, we get less REM sleep, and its function is still not entirely clear. It’s thought to be key to memory formation, but people who take antidepressants spend far less time in REM sleep, and that doesn’t seem to consistently affect their memory. Also, it’s a myth that we only dream during REM sleep. Our most vivid dreams occur during REM sleep, but dreaming can occur at any stage of sleep.
Sleep paralysis is an inability to move that happens sometimes for a short period as you’re falling asleep or waking up. The mind is awake, but the body lags behind for a minute or two.
Although the feeling is bizarre and can be scary, sleep paralysis isn’t rare or dangerous. It occurs most often in young people, beginning in the teens, and in people with other sleep issues, including narcolepsy, sleep apnea, and nighttime leg cramps. It is also more common in people with post-traumatic stress or panic disorder. In those moments of paralysis, some people feel that they are falling, floating, or having an “out-of-body experience.” Others hallucinate a presence in the room, hovering nearby, and may conclude they have been abducted by aliens or visited by ghosts. According to one theory, people who feel outside of their own bodies or sense ghostly presences might be experiencing a glitch in their mirror neurons, the part of the brain that fires when we observe activity in other people.
We’ve all heard people boasting that they’re perfectly functional on five hours of sleep or less. Adults do vary in their sleep needs, but the number who are at their best with such little sleep is vanishingly small. Long-term sleep deprivation is linked to obesity, type 2 diabetes, heart disease, and traffic accidents.
So why do people say they’re fine on a sleep-deprived schedule? A rush of cortisol, the hormone that revs us up to manage stress, can create the sensation of alertness. It’s an illusion; the sleep-deprived still do poorly on objective tests of their short-term memory and motor skills.
For optimal functioning, seniors usually need seven to eight hours, and other adults need seven to nine. Teens need eight to 10 hours and younger children need even more. People who are getting enough sleep take at least 15 minutes to fall asleep when they get into bed.
Although losing an entire night’s sleep zombifies most of us, there are exceptions: Some people feel much happier or calmer after an all-nighter.
That’s probably because the jolt is a reset for their body clocks, which were out of whack, an idea first described in an 1818 German psychiatric textbook.
Depression or bipolar disorder almost always involves a disruption in sleep, which may be a symptom or a trigger. According to British psychiatrist David Veale, staying up for 36 hours relieves mood symptoms in about half of these patients. To maintain this state, he prescribes a sleep schedule that requires waking up in the wee hours for the next several days. After that, they may be able to stay in a more standard sleep schedule, supported by light therapy. Our body clocks are set by light: Veale prescribes exposure to intense white light in the morning for six months to a year.
The last Guinness World Record for staying awake went to 17-year-old Randy Gardner, after he stayed awake for 11 days and 25 minutes in 1963 — but even if you decide to risk grievous bodily harm by exceeding it, nobody’s going to record your victory. The health risks are so vast after even a few days without sleep that Guinness did away with the record because of how dangerous it would be to attempt it.
Gardner, who drafted friends to help him stay awake in shifts, said it became very difficult on his third day of wakefulness, and he ate tangerines and oranges to help with the nausea he experienced. Eventually, a Stanford researcher took notice and kept him company for the rest of the record-breaking run. After he hit his milestone, he fell asleep with electrodes attached to his head at a nearby naval hospital. He and his friends won first place in the Greater San Diego Science Fair for their efforts.
A siesta can be any nap or short rest — or it may refer to a specific time of the day set aside for naps, particularly in (but not limited to) Spain. While the tradition has fallen by the wayside for many people in the modern world, it’s codified in at least one place. In Ador, Spain, a small town near Valencia, the hours between 2 p.m. and 5 p.m. are an official quiet time. Businesses close, sports pause, and parents are encouraged to keep their children inside. A siesta between 3 p.m. and 5 p.m. is still standard practice in parts of Greece as well, especially during the hot summer months.
The word “siesta” comes from the Latin term “hora sexta,” used in ancient Rome to refer to the sixth hour after dawn — typically the start of a period of rest.
Artificial light has made sleep far less pleasant. We get too little sunlight and too much light when we need darkness.
In medieval Europe, there were no glowing smartphones or bedside lamps. At sundown, families blew out a candle and retreated to soft heaps of rags in one room. After about four hours of sleep, at midnight, adults awoke for a blissful hour or two of prayer, sex, reading, writing, or chatting, before they dozed off and awoke at dawn.
That’s apparently the natural rhythm. In an experiment in the 1990s, in which participants lived away from artificial light, after three weeks they gradually drifted into the pre-artificial light pattern of waking in the middle of the night. Tests of their blood in the interlude showed that even without sex, they were awash in prolactin, a hormone released after orgasm that gives us the “afterglow.”
Eight hours seems to be the key, but ideally, we’d all have a sweet interlude. Just don’t turn on your lights or use your laptop or phone.