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For as long as she can remember, Aimee Pugh Bernard hasn't needed much sleep. Currently, he usually goes to bed around 10:00 p.m. and wakes up around 4:30 a.m. "I'm wide awake. I can't stay in bed," she says.
Sometimes Bernard—a professor of Immunology at the University of Colorado, United States—can't fall asleep right away. In those cases, he barely sleeps five hours.
The most surprising thing is that, the next day, Bernard usually feels full of energy. He walks his dog, does an intense one-hour workout at the gym, and completes an hour and a half of work before 8:00.
His friends are amazed at his ability to do so much with so little sleep.
However, in his family this is normal: both his father and his brother are the same.
Most of us, of course, need more.
According to the most recent review of scientific evidence by the US National Sleep Foundation, the average adult between the ages of 26 and 64 requires between seven and nine hours of sleep per 24 hours.
The reason for such a wide variation in each person's sleep needs has long been a mystery.
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However, in recent years, scientists have identified several ways in which genetics influences this aspect.
From rare mutations—like the one Bernard has—to hundreds of much more common variants, there are explanations for why some people can function well on very little sleep.
In the future, these findings could serve to protect those who do not get enough sleep, helping them avoid some of the common consequences of lack of sleep.
The first clues
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In 2019, Bernard discovered the possible cause of his particular sleep-related "superpower."
A research team from the University of California, San Francisco, USA, identified a genetic mutation linked to sleep duration in humans.
Although people carrying this mutation went to bed at fairly conventional times, they woke up very early, generally sleeping between four and six and a half hours each night.
After sending a blood sample to the research team, Bernard knew she was one of those people.
This rare, inherited condition is called "familial natural short sleep" (FNSS). Since then, other mutations associated with FNSS have been identified.
One of the biggest mysteries surrounding FNSS is that those with it seem to be "fine" despite getting so little sleep, says the team's lead researcher, molecular biologist Ying-Hui Fu.
The exact reasons are still being studied.
There is fascinating evidence that genetic variations linked to FNSS not only cause a reduced need for sleep, but also protect those who have them against the consequences of lack of rest, such as memory impairment.
In an experiment conducted in 2019 under Fu's direction, a mutation related to FNSS was introduced into mice.
The team observed that mice carrying this variant not only slept less, but also seemed to be protected against memory deficits.
Another test revealed that mice with some of these variants were less likely to develop a version of Alzheimer's disease in this species.
In 2014, an international research team studied a pair of dizygotic twins (twins), in which one of them had a mutation associated with short sleep, while the other did not.
It was observed that the carrier twin usually slept approximately one hour less than his brother.
They also discovered that by keeping both twins awake continuously for 38 hours, the carrier twin recorded about 40% fewer performance failures than the other twin.
The researchers also found interesting differences in the way the twins slept.
Although the carrier twin slept less, his amount of non-REM sleep—which includes slow-wave sleep or "deep sleep"—was virtually the same as his brother's.
This could mean that, in some ways, he was getting more benefits from the time he spent sleeping.
Pharmaceutical dreams
However, research in this field continues, and is essential, says Fu.
In recent years, there has been growing interest in how our knowledge of these genetic variations could be harnessed to help people.
In the pharmaceutical industry, there is hope that one day discoveries about people who need little sleep could lead to the development of drugs to treat sleep disorders or, for example, help military personnel function on less sleep.
To do this, scientists not only need to be clear about whether these variants protect short sleepers from negative consequences, but also understand exactly how they do so.
Without this information, you risk creating a drug with unexpected side effects.
"You have to understand how it works," says Fu. "You wouldn't want to sleep less and, after five, ten or 20 years, end up developing Alzheimer's, Parkinson's or cancer."
While the genetic mutations associated with FNSS are one of the most extreme and fascinating examples, they represent only a small part of the genetic factors that can determine the duration of our sleep.
In general, it is estimated that the duration of our sleep has a heritability of between 30% and 65%; This means that up to 65% of the differences in sleep duration between people can be explained by genetics.
To date, several hundred regions have been identified in the genome that influence sleep duration.
A recent analysis, which examined data from nearly 650,000 adults, identified about 244 such regions. (This research has not yet been published and is currently in the pre-publication phase.)
According to the lead author of the study, geneticist Isabelle Austin-Zimmerman, from King's College London, if we analyze each of these common mutations separately, we see that they are only associated with a difference of approximately one minute in sleep duration.
However, when combined, their effects can accumulate. Austin-Zimmerman points out that, in the average person, genetic differences could explain about a 20-minute variation in sleep duration.
However, there is still not much research into which of these more common variants could protect people from the effects of insufficient sleep.
Still, a recent study led by Chiara Petrosellini, a clinical academic obstetrician and gynecologist at University College London, found evidence of one of these variants.
The research team analyzed the genetics of 343 women with bipolar disorder who gave birth.
Their genetic profile was evaluated to determine the likelihood that they were low-sleep individuals, based on the presence of mutations suspected to be involved in this trait.
Those with a greater predisposition to need little sleep had half the risk of developing postpartum psychosis compared to women who had a lower predisposition to this trait.
A similar trend was observed for insomnia.
Although more studies are needed, the researchers suggest that these people may have developed, over the course of their lives, a greater tolerance for sleep disruption.
This could be mitigating the impact that lack of sleep—common in the postnatal period—has on your mood.
However, unfortunately, having a genetic predisposition to short sleep is not always beneficial.
In fact, research conducted by Austin-Zimmerman and her team in a much larger population (not limited to mothers with bipolar disorder) revealed that genetic variants associated with shorter sleep duration generally lead to a higher risk of insomnia and fatigue.
They have also been linked to various physical and mental health problems, including ADHD, depressive symptoms and type 2 diabetes.
This does not necessarily mean that insufficient sleep—or having a predisposition to do so—is the cause of these conditions. But it does imply that a genetic predisposition to little sleep does not always protect against these risks.
The illusion of being well
To complicate matters further, even those of us who believe we function well on light sleep are not always the best judges of our own situation.
One study, for example, found that when healthy adults were limited to four or six hours a night in bed, their performance on various cognitive tests progressively worsened.
However, after two weeks, participants reported feeling only "slightly" sleepy.
"Your ability deteriorates more and more, but at the same time, you are less and less aware of that deterioration," explains Hans van Dongen, a sleep researcher at Washington State University's Sleep and Performance Research Center and co-author of the study.
It is true that many people need less hours of sleep than others. Other research, carried out by Van Dongen himself, has shown that there are individuals more resistant to lack of sleep.
However, this means that understanding such differences is more complex than simply asking how many hours someone sleeps or how they feel the next day.
In the long term, genetic findings like those of Austin-Zimmerman and Fu could help identify people who really function well on short sleep.
They could also serve to distinguish those who, although they feel well, are actually at greater risk of suffering a deterioration in their abilities.
Over time, these discoveries are expected to lead to the development of drugs that help short sleepers strengthen their resistance to sleep deprivation.
In the meantime, these findings may help people understand why they sleep the way they do.
In Bernard's case, knowing that he carried one of the genetic variants associated with natural short sleep helped relieve some pressure, he says.
As a scientist, I already knew that there are natural variations among humans, even when it comes to sleep.
Plus, she's always valued the extra time this gives her to get through her workday, especially when her husband and kids are still fast asleep.
Still, Bernard wondered if he was simply having a hard time relaxing, or if his inability to sleep more was a sign that he was trying to take on too much.
"Now I have an answer," says Bernard. "I know that, genetically, that's who I am; and I'm just going to have to accept it."
*This article was published on BBC Future. Click here if you want to read the original version (in English).
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