Credit, Getty Images
For as long as we've known each other, Aimee Pugh Bernard hasn't needed much sleep. Currently, she usually goes to bed around 10 pm and wakes up around 4:30 am. "I can't stay in bed anymore," she says.
Bernard is a professor of immunology at the University of Colorado, in the United States. Sometimes she can't fall asleep right away, and when she does, she only sleeps for five hours.
The most surprising thing is that, the next day, Bernard usually feels full of energy. She takes the dog for a walk, does an intense hour-long workout at the gym, and works out for an hour and a half, all before eight in the morning.
Your friends are amazed at your ability to do so much on so little sleep. But in your family this is normal: your father and brother lead equal lives.
But of course most of us need more sleep.
The most recent review of scientific evidence, carried out by the US National Sleep Foundation, indicates that the average adult, aged 26 to 64, needs seven to nine hours of sleep every 24 hours.
Why people's sleep needs vary so widely has long been a mystery. But in recent years, scientists have identified several ways in which genetics influences this aspect.
From rare mutations, like the one presented by Bernard, to hundreds of much more common variants, explanations have emerged as to why some people can function well on very little sleep.
End of Most read
In the future, these findings could serve to protect people who can't get enough sleep, helping them avoid some of the usual consequences of lack of sleep.
The first clues
Watch news from Brazil and the world on the BBC World Service
Download here
End of app promotion
In 2019, Bernard discovered the possible cause of his sleep-related “superpower”.
A research team from the University of California in San Francisco, USA, has identified a genetic mutation linked to sleep duration in humans.
People with this mutation go to bed at fairly conventional times, but wake up very early, generally sleeping four to six and a half hours a night.
Bernard sent a blood sample to the research team and learned that he is one of those people.
This is a rare and hereditary condition called "familial natural short sleep" (FNSS). Since then, other mutations associated with FNSS have been identified.
One of the biggest mysteries regarding FNSS is that people who have the condition seem to be "fine" even when they sleep little, according to the team's lead researcher, molecular biologist Ying-Hui Fu.
The exact reasons are still the subject of study.
There is evidence that genetic variations linked to FNSS not only cause less need for sleep, but also protect their carriers against the consequences of lack of rest, such as memory deterioration.
In an experiment carried out in 2019 under Fu's direction, a mutation related to FNSS was introduced into mice.
The team observed that mice carrying the aforementioned variant not only slept less, but also appeared 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 characteristic of their species.
In 2014, an international research team studied a pair of dizygotic (fraternal) twins. One of them had a mutation associated with short sleep, and the other did not.
It was observed that the carrier twin usually slept about an hour less than his brother.
The researchers also found that by keeping both twins awake continuously for 38 hours, the carrier sibling experienced about 40% fewer performance failures than the other.
Curious differences were also observed in the way the two slept. The carrier twin slept for less time, but the duration of his non-REM sleep (which includes slow-wave sleep or "deep sleep") was about the same as his brother's.
This could mean that, in a way, he derived greater benefits from his period of time dedicated to sleep
Medicinal sleep
But research in this field continues and is fundamental, highlights Fu.
In recent years, interest has increased in how our knowledge of these genetic variations could be used to help people.
In the pharmaceutical industry, there is hope that, someday, discoveries about people who need little sleep could lead to the development of pharmaceutical products to treat sleep disorders or, for example, to help military personnel get through the day with fewer hours of sleep.
To do this, scientists not only need to know for sure whether these variants protect people who sleep little against negative consequences, but also understand exactly how they work. Without this information, you run the risk of creating a pharmaceutical product with unexpected side effects.
“You need to understand how this works,” says Fu. "You don't want to sleep less and, after five, 10 or 20 years, end up developing Alzheimer's, Parkinson's or cancer."
The genetic mutations associated with FNSS constitute one of the most extreme and fascinating examples, but they represent only a small part of the genetic factors that can determine the length of our sleep.
In general, it is estimated that the time we spend sleeping is hereditary in 30% to 65%. In other words, up to 65% of differences in sleep duration between people can be explained by genetics.
Hundreds of regions of the genome that influence sleep duration have been identified.
A recent analysis examined data from nearly 650,000 adults and identified about 244 of these regions. This research has not yet been published and is currently in the pre-publication phase.
The main author of the study, geneticist Isabelle Austin-Zimmerman, from King's College London, indicates that, if we analyze each of these common mutations separately, we observe that they are only associated with a difference of around one minute in sleep duration. But their combined effects can accumulate.
Austin-Zimmerman highlights that, in an average person, genetic differences could explain variations of around 20 minutes in sleep duration.
But there still isn't much research into which of these more common variants could protect people against the effects of lack of sleep.
Still, a recent study led by gynecologist and obstetrician Chiara Petrosellini, a clinical academic at University College London, found evidence of one of these variants.
The research team analyzed the genetics of 343 women with bipolar disorder who had given birth. Their genetic profile was evaluated to determine the probability that they were people who need little sleep, based on the presence of mutations that, according to suspicion, intervene in this characteristic.
People with a greater predisposition to needing little sleep had half the risk of developing postpartum psychosis, compared to women who were less predisposed to this characteristic.
In the case of insomnia, a similar trend was observed.
More studies are needed, but researchers suggest that these people may have developed, throughout their lives, greater tolerance to sleep interruption.
This situation can reduce the impact of lack of sleep in the postnatal period on your mood.
But, unfortunately, having a genetic predisposition to sleep little is not always beneficial.
Research by Austin-Zimmerman and her team in a much broader population (not limited to mothers with bipolar disorder) revealed that, in general, genetic variants associated with shorter sleep duration carry a higher risk of insomnia and tiredness.
They have also been linked to several physical and mental health problems, such as ADHD, depressive symptoms and type 2 diabetes.
This conclusion does not necessarily mean that sleeping little (or having a predisposition to it) is the cause of these conditions, but it does indicate that the genetic predisposition to sleep little does not always protect us against these risks.
The illusion of being well
To make things even more difficult, even people who believe they function properly on little sleep are not always the best judges of their condition.
A study revealed that, by limiting the time in bed of healthy adults to just four or six hours a night, their performance on several cognitive tests was progressively reduced.
But after two weeks the participants said they felt only "slightly" drowsy.
"Your capacity deteriorates more and more, but at the same time you are less and less aware of this deterioration," explains sleep researcher Hans van Dongen from the Sleep and Performance Research Center at Washington State University in the US. He is one of the authors of the study.
The truth is that many people need fewer hours of sleep than others. And new research, carried out by Van Dongen himself, has shown that there are individuals who are more resistant to lack of sleep.
But this means that understanding these differences is more complex than simply asking a person how many hours they sleep or how they feel the next day.
In the long term, genetic discoveries like those by Austin-Zimmerman and Fu could help identify people who actually function well on little sleep. And they could also serve to differentiate those who, despite feeling well, are actually at greater risk of suffering a deterioration in their capabilities.
Over time, it is hoped that these findings will lead to the development of pharmaceuticals that help people who sleep little to strengthen their resistance to lack of sleep.
For now, these discoveries can help people understand the reasons for the way they sleep.
For Bernard, knowing that she carries one of the genetic variants associated with FNSS helped her alleviate some of the pressure about it.
As a scientist, she already knew that there are natural variations among human beings, including in relation to sleep. She has also always valued the extra time this condition has given her to bring forward her workday, especially when her husband and children are still asleep.
Still, Bernard wondered if she simply had a hard time relaxing, or if her inability to sleep was a sign that she was trying to centralize too many tasks.
"Now, I have an answer," she explains. "I know that, genetically, that's how I am. And I'm just going to have to accept that."
Read the original version of this report (in English) on the BBC Future website.
Discover more
Watch
End of Watch
