Why Do Some People Thrive on So Little Sleep?

Everyone has heard that it’s essential to get seven to nine hours of sleep every night, a recommendation that has been repeated so often that it has become sacrosanct. If you get less than that, you’re more likely to suffer from short- and long-term ill health — memory problems, metabolic problems, depression, dementia, heart disease, and a weakened immune system.

But in recent years, scientists have discovered a rare breed that doesn’t close its eyes as much and is no worse for wear.

Natural short sleepSleepers, as they’re called, are genetically predisposed to need only four to six hours of sleep a night. These outliers indicate that quality, not quantity, is what matters. If scientists can figure out what these people do differently, they hope to provide insight into the nature of sleep itself.

“The bottom line is that we don’t understand what sleep is, let alone its purpose. This is incredible, considering that the average person sleeps a third of their life.” Louis Ptaceka neurologist at the University of California, San Francisco.

Scientists once thought He sleeps It was nothing more than a break, like turning off the computer in preparation for the next day’s work. Thomas Edison described sleep as a waste of time.A legacy from our cave days“He claimed to never sleep more than four hours a night. His invention of the incandescent lamp encouraged shorter sleep times for others. Today, a historically large number of adults in the United States sleep less than five hours a night.

But recent sleep research has shown that sleep is an active and complex process that we don’t necessarily want to shortchange. While we sleep, scientists suspect our bodies and brains do as well Replenishing energy stores, Expel waste and toxinspruning of synapses and Consolidation of memories. As a result, chronic sleep deprivation can occur Serious health consequences.

Most of what we know about sleep and sleep deprivation stems from a model proposed in the 1970s by a Swiss-Hungarian researcher named Alexander Borbely. for him Two-process model Sleep describes how separate systems—circadian rhythm and sleep homeostasis—interact to control the time and duration of our sleep. the Biological clock It dictates the 24-hour sleep-wake cycle, guided by external cues such as light and darkness. Sleep homeostasis, on the other hand, is driven by internal stress that builds while you’re awake and decreases while you sleep, ebbing and flowing like hunger.

There is a difference in these patterns. “We’ve always known that there are morning birds and night birds, but most people fall in between. “We’ve always known that there are short sleepers and long sleepers, but most people fall in between,” Ptacek says.. “They were there, but the reason they weren’t recognized is because these people generally don’t go to doctors.”

That changed when Ptacek and his colleague changed Ying Hui Fua human geneticist and neuroscientist at the University of California, San Francisco, identified a woman who felt her early sleep schedule had changed It was a curse. It is normal for a woman to wake up in the early hours of the morning, when it is “cold, dark and lonely.” Her granddaughters inherited the same sleeping habits. The researchers determined Genetic mutation of this rare species of morning lark, After they published their findings, thousands of early risers walked out of work.

But Fu remembers being fascinated by one family that didn’t fit that mold. These family members woke up early but did not go to bed early, and felt refreshed after only about six hours of sleep. They were the first to be identified with familial short sleep, a condition that runs in families like other genetic traits. Fu and Ptacek traced their brief slumber to a Mutation in a gene called DEC2.

The researchers went on to genetically engineer the DEC2 mutation into mice, showing that the animals needed less sleep than their peers. And they found it One of the gene’s functions is to help control levels of a brain hormone called orexinWhich enhances alertness. Interestingly, orexin deficiency is the main cause of narcolepsy, a sleep disorder characterized by episodes of excessive daytime sleepiness. However, orexin production appears to be increased in people with short sleep durations.

Over time, the team identified seven genes associated with normal short sleep. In one family with three generations of short sleepers, researchers found A Mutation in a gene called ADRB1It is highly active in an area of ​​the brainstem, the dorsal pons, which is involved in regulating sleep. When scientists used a technique to stimulate this brain area in mice, to wake them from sleep, the mice with the ADRB1 mutation woke up more easily and stayed awake longer.

In a short-sleeping father-son pair, researchers identified A Mutation in another gene, NPSR1Which is involved in regulating the sleep-wake cycle. When they created mice with the same mutation, they found that the animals spent less time sleeping and, in behavioral tests, lacked the memory problems that typically follow a short night’s sleep.

The team also found two distinct mutations in… The gene is called GRM1in two unrelated families with short sleep cycles. Again, mice genetically modified with these mutations slept less, with no apparent health consequences.

Like mice, people who are naturally short sleepers appear to be immune to the ill effects of sleep deprivation. If anything, They are doing a very good job. Research suggests that these people are ambitious, energetic and optimistic, with remarkable resilience to stress and higher pain thresholds. And they may live longer.

Based on the findings in short sleep, some researchers believe it may be time to update the old two-process model of sleep, which is how Ptacek developed the idea of ​​a third effect. The updated model might unfold as follows: In the morning, your biological clock signals that it’s time to start your day, and sleep balance signals that you’ve gotten enough sleep to get out of bed. Then there is a third factor – behavioral motivation – that forces you to go out and do your work, find a mate, or gather sustenance. At night, the process goes in reverse, calming the body for sleep.

Perhaps short sleepers are so driven that they are able to overcome the innate processes that keep others in bed. But it may also be the case that, somehow, short sleepers’ brains are built to sleep so efficiently that they are able to do more with less.

Active sleep

“It’s not as if there’s something magical about your seven to eight hours,” he says. Phyllis Zdirector of the Center for Circadian and Sleep Medicine at Northwestern University. Zee can imagine countless ways short sleepers’ brains could be made more efficient. Do they enjoy more slow-wave sleep, the most restorative stage of sleep? Are they generating greater amounts of cerebrospinal fluid, the fluid that bathes the brain and spinal cord, enabling them to get rid of more waste? Is their metabolic rate different, helping them get in and out of sleep more quickly?

“It’s all about efficiency, sleep efficiency, that’s how I feel,” Fu says. “Whatever their body needs while sleeping, they can do it in a short time.”

Recent studies by Fu and Ptashek suggest that people with naturally short sleep duration may be more efficient at removing toxic brain aggregates that contribute to neurodegenerative disorders such as Alzheimer’s disease. The researchers bred mice that had short He sleeps Genes found in mice that carry genes that predispose them to Alzheimer’s disease. Mice with Alzheimer’s developed a buildup of abnormal proteins — amyloid plaques and tau tangles — that are hallmarks of dementia in humans. But the brains of the hybrid mice developed fewer of these tangles and plaques, as if the sleep spikes were protecting the animals.

Fu believes that if she conducted similar studies in models of heart disease, diabetes, or other diseases linked to sleep deprivation, she would obtain similar results.

The deepest secrets of sleep

It’s not yet clear how the short sleep genes identified so far protect people from the ill effects of poor sleep, or how mutations in these genes make sleep more efficient. For the answer, Fu and Ptashek They began by bringing short sleepers into their shared laboratory to measure their brain waves while they slept. Their sleep study was derailed by the COVID-19 pandemic, but they are eager to get it back on track.

Researchers are also interested in understanding other sleep outliers. Sleep duration, like most behaviors, follows a bell curve. Short sleepers sit on one end of the curve, and long sleepers on the other. Fu discovered a genetic mutation associated with long sleep, but long sleepers are difficult to study because their schedules do not conform to society’s standards and demands. People who sleep for long periods often have to wake up early to go to school or work, which can lead to sleep deprivation and may contribute to depression and other illnesses.

But even though his sleep is strong The genetic component, can also be shaped by the environment. Knowing that better sleep is possible, and understanding the basis, can pave the way to interventions to improve sleep, enabling more people to live longer, healthier lives.

Z Lab, for example, modified its use Audio stimulation To promote deep slow-wave sleep, which enhances memory processing and may be one of the secrets to the success of people who sleep for short periods. In one study, they played pink noise — a softer, more natural sound than white noise, and closer to rain or the ocean — while study participants slept. The next day, these participants remembered more on a test of learning and recalling word pairs. “We can boost memory, but we don’t necessarily make them sleep longer or shorter,” says Zee. “I think there is a lot to learn.”

For now, researchers recommend that people focus on getting the amount of sleep they need, recognizing that it will be different from person to person. Ptacek still gets angry when he hears someone preach that everyone should sleep eight hours a night. “That’s like saying every member of the population should be 5 feet 10 inches tall,” he says. “That’s not how genetics works.”

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