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A lack of sleep leads to all kinds of physical and mental health problems. But as we’ve realized how important sleep is, we’ve begun making all sorts of hyper-specific recommendations around it. Many of those recommendations, however, are wrong—and doing more harm than good.
If humans don’t sleep enough, we turn into unhealthy, unstable people. Many studies have pointed us to this fact however we know this is true from our own personal experiences.
Lack of sleep is associated with all kinds of poor health outcomes.
But as we’ve learned how vital sleep is to keep humans physically and mentally well, we’ve begun to push sleep into the common trap we do with all good behaviours. We started making very specific recommendations around it.
Suppose you were to ask someone about sleep and sleeping better. They’d probably fire off a series of rules perfect sleep requires: you must sleep a certain amount of time at a certain temperature inside a room designed to mimic a black hole.
So let’s dive into six big sleep myths.
There’s no strong evidence that eight hours is best. Most people sleep seven hours and, in fact, sleeping 7-ish nightly hours was associated with the lowest risk of death.
Eight hours a night is the oldest myth in the book.
Researchers in the Anthropology department at Harvard analysed a range of studies on this. Their takeaway: “Most adult Westerners probably average about seven hours a night, a good hour (13 percent) less than the eight hours we supposedly need.”
And the amount of sleep the average person gets changes depending on their age and the season. For example, Westerners sleep an average of 6.5 hours in the summer and 7.5 hours in the winter.
Of course, many Westerners are unhealthy. So you might think our lack of health is due to getting less than eight hours. People often point out that our sleep is disturbed by technology like TVs, smartphones, alarm clocks, etc.
But a study put sleep trackers on people from three different pre-industrial tribes from Tanzania, Namibia, and Bolivia. None of these tribes have electricity or smartphones, and all three of these tribes don’t seem to get the chronic diseases that kill most Westerners, like heart disease.
The scientists assumed that without electronics keeping them awake, the tribe members would sleep eight solid hours. And that would be one explanation for their great metabolic health.
They found the tribe members averaged between 5.7 and 7.1 hours a night. That’s less than us. Like us, they slept less in the warm summer months (5.7 to 6.5 hours/night) and more in the winter months (6.6 to 7.1 hours/night).
Scientists first realized that eight hours was probably a myth in 2002. That’s when researchers analysed health and sleep data from one million people. They found that people who slept eight hours had 12 percent higher death rates than people who slept 6.5 to 7. The study was controversial since the sleep data was self-reported.
But the research has been piling up ever since. It suggests people who sleep seven-ish hours a night have the lowest risk of all-cause mortality. What’s more, it actually seems bad to get more than eight hours.
As the same Harvard anthropologists put it:
“(Westerners) who sleep about seven hours tend to live longer than those who sleep more or less. In no study is eight hours optimal, and in most of the studies people who got more than seven hours had shorter life spans than those who got less than seven hours (an unresolved issue, however, is whether it would be beneficial for long sleepers to reduce their sleep time.)”
If you regularly sleep eight or even nine hours, don’t freak out. There are many factors at play here. The point is, rather, eight hours isn’t magic.
Some people sleep better in darkness and silence. Others benefit from some light and noise, like having a TV on in the background. If early humans couldn’t sleep without disturbances, we would have never slept.
The conclusion of Carol Worthman, one of the greatest anthropologists of our time and the world’s foremost expert studying how different cultures sleep and how humans likely slept across our evolution was:
Still today, some noise and light help many people nod off. Some people like to fall asleep with the TV on—it helps them sleep better. This makes sense, given Worthman’s findings.
Worthman also shows that people can adapt to sleeping in light and sound. If we couldn’t sleep at all with sound around us, even some loud sounds, densely packed cities wouldn’t exist.
Obviously you can’t have an air raid siren going off and a strobe light in front of your face all night.
But the lesson here is to figure out what environment you sleep best in. Experiment—and don’t try to force darkness and silence if it’s not helping you.
Research suggests sleeping pills work by placebo and have clear health harms.
As far back as the 1970s, a researcher noticed that people who took sleeping pills had a greater mortality rate than those who didn’t. But it was a chicken and egg problem. Was their lack of sleep hurting them, or was it the pills?
They have been looking into prescription sleeping pills ever since. In a massive 2010 study, they found taking sleeping pills “was associated with greater than threefold increased hazards of death … in 2010, hypnotics may have been associated with 320,000 to 507,000 excess deaths in the US alone.”
The study was observational; the researchers didn’t say sleeping pills directly caused these deaths. But they did write, “The consistency of our estimates across a spectrum of health and disease suggests that the mortality effect of (sleeping pills) was substantial. Even 10,000 yearly excess deaths caused by hypnotics would be too many.”
Funny enough, sleeping pills seem to work mainly by placebo effect. That’s according to a study. It found that people prescribed the pills slept the same length as those prescribed a sugar pill.
When asked why they didn’t do a more stringent randomized controlled trial of sleeping pills, they wrote, “Perhaps for reasons similar to the absence of randomized trials of cigarettes and of skydiving without parachutes.”
One sleep researcher at UCLA thinks we’ll eventually view prescription sleeping pills like we do cigarettes.
Sleep restores your brain more than your body. Getting a bad night’s sleep hurts some but not all types of athletic performance.
Obviously sleep does rest our bodies, but so does, say, laying on the couch and watching the Olympics. There isn’t strong research suggesting that muscle repair after a big workout is vastly more powerful during sleep versus lounging.
Scientists found that a bad night’s sleep can hurt athletic performance. But it depends on what kind of performance. Activities with a strong mental component are hurt most.
For example, bad sleep doesn’t impair strength because lifting is often a quick, semi-mindless act. Bad sleep does seem to impact accuracy and lead endurance athletes to tap out earlier (this is probably because elite endurance sports are more of a mental than a physical game at the higher levels).
And so, researchers wrote, “It doesn’t take a lot of brainpower to realise that sleep is mostly about the brain.”
There seem to be two ways sleep helps our brain.
But because our brain is tightly sealed off, it can’t seem to get rid of these metabolites as it’s up and running while we’re awake.
Picture this like a car running at idle in a garage. But pretend the car’s engine can’t run with the garage door open. So across the day, the engine runs in the closed garage, and smog builds and builds in the brain. Run the engine too long with the garage door closed, and you get a dangerous smog build up.
As we sleep, it’s like the engine shuts off and the garage door opens. During certain sleep phases, some areas of our brain expand by 60 percent, which allows the previous day’s metabolites to clear. This also lets in enzymes that repair and rejuvenate receptors in the brain. Sort of like having a mechanic come in to tune the engine while the garage is open and the engine is “off.”
The researchers wrote, “For every hour spent awake storing memories and amassing waste, we need approximately fifteen minutes asleep to process those memories and clean up.” Like all specific numbers, the researchers note, it’s an average. Some people need more than fifteen minutes, others less, depending on age.
Many of us seem “programmed” to wake at night. And that’s OK! What’s bad is worrying when you wake up in the middle of the night. That anxiety over lost sleep can impact your ability to fall back asleep.
Carol Worthman, the anthropologist who studies sleep patterns across cultures, has also discovered that throughout history, it’s been common for different societies to have two phases of sleep. Basically: many people wake up in the middle of the night and chat or even work for an hour or so, then go back to sleep.
Many Westerners, as well as different pre-industrial populations, do this. Importantly, these people don’t seem to be any worse off than people who sleep uninterrupted.
We all have our own sleep patterns, and some studies suggest a very good reason for this.
Researchers tracked the sleeping habits of 33 Hadza hunter-gatherers for 20 days. They found that there were only 18 minutes when all 33 people were asleep simultaneously. That’s not 18 minutes in one night—that’s 18 minutes across 20 nights.
On average, there were usually about eight tribe members awake at any given point in the night.
This is a normal and beneficial phenomenon. Here’s why we evolved to all have different sleep habits:
Another sleep researcher said that these mid-night wake-ups may have also given us a relaxing time to destress and meditate on our dreams and emotions.
Hence, we all still sleep differently.
The problem with giving hyper-specific rules around sleep is that it can cause anxiety. “Many people wake up at night and panic (that they’ve woken up),” a neuroscientist at Oxford told the BBC. “I tell them they are experiencing a throwback to the bi-modal sleep pattern.”
REM sleep still perplexes sleep scientists. We don’t have enough evidence to suggest that trying to time and alter our sleep cycles with sleep devices helps at a population level. (But please continue this if you’re doing it and it helps you.)
You may have heard you should time your REM sleep cycles.
This appears largely to be a theory invented by people who don’t study sleep. When the world’s top sleep researchers recently met at a conference, they called REM sleep “the proverbial riddle wrapped in a mystery inside an enigma.”
If humans couldn’t function unless our sleep cycles were perfectly timed, we’d have all died off.
Imagine that it’s 200,000 years ago, and we’re asleep. We’re only 47 minutes into our final 90-minute sleep cycle. But then we get woken up by a tiger who has come into our camp because it wants a midnight snack.
If we couldn’t perform well no matter what point in our sleep cycle we’d woken up, we’d have a very negative experience.
Timing sleep cycles seems to be one more way the rise of hyper-specific health recommendations makes our lives more finicky and anxious rather than better.
If you’re doing this and it helps you, please continue. But do make sure the practice doesn’t become a liability. People who practice specific routines often fall apart when their routine doesn’t go perfectly. Being resilient to change makes you a more versatile and effective human.
There are more myths out there. But those six seem to be the most common.