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For as long as she can remember, Prof Aimee Pugh Bernard hasn't needed much sleep. She usually goes to bed around 22:00 and wakes up around 04:30.
"I was completely awake and couldn't stay in bed," she said.
There were days when she couldn't fall asleep right away, sleeping only five hours in total, but still had plenty of energy the next day. She takes the dog for a walk, completes an hour of intense exercise in the gym, and accumulates an hour and a half of work time by 08:00.
She is a professor of immunology at the University of Colorado, and friends are amazed that she gets so much done on so little sleep. But it was normal in her family, as it was the same with her father and brother.
Bernard is in the minority, most of us need more sleep.
The average adult aged 26 to 64 needs about seven to nine hours of sleep every 24 hours, according to the latest evidence review from the National Sleep Foundation.
Why people vary greatly in the amount of sleep they need has been a long-standing mystery. Over the past few years, scientists have identified genetic factors as an important factor.
The pharmaceutical industry hopes to find clues and develop new drugs to treat patients with sleep disorders.
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Not only does it shorten your sleep time, it also prevents memory damage
In 2019, Bernard learned the possible reason why he has this "superpower" of sleep.
A research team at the University of California, San Francisco has discovered a genetic mutation associated with sleep duration in humans.
People with this mutation usually go to bed at a normal time, but they wake up very early and tend to get only four to six and a half hours of sleep each night. After Bernard sent a blood sample to the research team, he discovered that he was one of them.
This rare and heritable condition is called familial natural short sleep (FNSS). Since then, scientists have discovered several mutations linked to natural short sleep in families.
Fu Yanhui, a molecular biologist and lead researcher on the research team, said that one of the biggest mysteries in the field is that people with familial natural short sleep seem to be "in good condition" on very little sleep, and the reason is still being studied.
Evidence shows that genetic variants associated with natural short sleep in families not only lead to shorter sleep duration but may also protect carriers from related consequences, such as impaired memory.
An experiment led by Professor Fu Yanhui from Taiwan in 2019 introduced a mutation related to the family's natural short sleep into mice. The team found that mice carrying the relevant mutation not only slept less but also appeared to be immune to memory deficits. Another test found that mice carrying some of these mutations were less likely to develop the murine version of Alzheimer's disease.
In 2014, an international team of researchers studied a pair of human fraternal twins, one of whom carried the short-sleep mutation and the other who did not. The study found that twins carrying the mutation slept about an hour less on average than their siblings.
The researchers also found that when both people were kept awake for 38 hours, the person carrying the mutation made about 40% fewer errors on performance tests than the other person.
The researchers also found some interesting differences in the sleep patterns of the two men. Although the mutant carrier slept less, his non-REM sleep was nearly identical to his brother's. These include slow-wave sleep, known as "deep sleep," which may mean he gets more benefit from limited sleep in some ways.
pharmaceutical industry dream
Fu Yanhui said that research in this field is still ongoing and is extremely important.
In the pharmaceutical industry, some hope that research on short sleepers will one day lead to drugs to treat sleep disorders or help military personnel function on less sleep.
To do this, scientists must not only understand whether these variants protect short sleepers from negative effects, but also understand the specific mechanisms. Without this information, drugs developed may have unintended side effects.
"You have to understand how it works," Fu said. "You don't want to sleep less and end up with Alzheimer's disease or Parkinson's disease or cancer 10, five or 20 years later."
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Benefits and Risks
Studies estimate that between 30% and 65% of sleep duration is genetically influenced.
In other words, up to 65% of the variation in sleep duration between people can be explained by genes. So far, researchers have identified hundreds of genomic regions that influence sleep duration.
Isabelle Austin-Zimmerman, a geneticist at King's College London, and her team say that for the average person, genetic differences may explain about 20 minutes of difference in sleep duration.
Research on whether these more common genetic variants can mitigate the effects of sleep deprivation is limited.
But a new study led by Chiara Petrosellini, a clinical academic obstetrician and gynecologist at University College London, has found some evidence. The research team analyzed the genetic data of 343 women with bipolar disorder (bipolar disorder) who had given birth.
Researchers assessed the likelihood that women would become short sleepers based on the presence or absence of mutations suspected to be associated with short sleep. The results showed that women with the highest scores, who were most likely to be short sleepers, had half the risk of postpartum psychosis as those with the lowest scores, and the same trend was seen for insomnia.
The researchers pointed out that more research is needed to confirm, but it is possible that these people have developed a higher tolerance for sleep disruption at an earlier stage in life. This may lessen the emotional impact of disturbed sleep after childbirth.
Unfortunately, being genetically predisposed to short sleep isn't always beneficial. In fact, Austin-Zimmerman and her team's study of a larger population (not specifically mothers with bipolar disorder) found that genetic variants associated with shorter sleep were associated with a higher risk of insomnia and fatigue in general.
These variants are also associated with a variety of mental and physical health conditions, including attention deficit hyperactivity disorder (ADHD), symptoms of depression, and type 2 diabetes.
This does not necessarily mean that short sleep, or susceptibility to short sleep, will lead to these illnesses. But it does mean that a genetic predisposition to short sleep does not always protect people from these risks.
The illusion of being safe
To complicate matters further, even if we think we can function well on sleep deprivation, we may not be the most reliable judges.
One study found that when healthy adults were limited to four or six hours a night in bed, their performance on cognitive tests continued to deteriorate.
However, two weeks later, participants still rated their sleepiness as only "slightly sleepy."
Hans van Dongen, a sleep scientist at Washington State University's Sleep and Performance Research Center, co-authored the study. He says you gradually experience more functional impairment, but at the same time you become less aware of it.
It remains true that many people do need less sleep than others. Other research by Van Dongen himself has found that some people are more resistant to sleep deprivation. But that means understanding the differences is more complicated than simply asking someone how many hours they slept or how they felt the next day.
In the long term, genetic research by people like Austin-Zimmerman and Fu may help identify people who actually function well on very little sleep. It can also identify people who think they are doing well but are actually at greater risk for functional impairment.
Eventually, it is hoped that these findings could lead to drugs that could help short sleepers increase their tolerance to sleep deprivation.
But until then, these findings can still help people understand why they sleep in certain ways.
Bernard said she was relieved to learn she carried one of the FNSS-related mutations. As a scientist, she already knew that people are inherently different, and the same goes for sleep. She has always cherished the extra time, which allowed her to start her day's work early while her husband and children were still asleep.
Even so, Bernard had wondered whether he was just particularly bad at relaxing, or whether his inability to sleep more meant he was taking on too many responsibilities.
"Now I have an answer," Bernard said. "I know that genetically, this is what I am, and I just have to live with it."
Amanda Ruggeri is a science, psychology and history journalist.
This article was originally written in English. We used artificial intelligence to assist in translation and was reviewed by BBC journalists before publication. Learn more about how we use artificial intelligence.
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