“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. But scientists still have plenty to learn about how.
What Is REM Sleep, Really?
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.
What Is Sleep Paralysis?
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.
It’s a Myth That Many Adults Only Need Five Hours of Sleep or Less
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.
But an All-Nighter Might Be Good for Your Mental Health
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.
Medieval Peasants Slept Better Than We Do
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.