Image source: María Medem/BBC
There are people who do not need to sleep for long hours, but it is difficult to know if you are one of them.
Amy Beau Bernard has never needed much sleep in her entire life. Currently, she often goes to sleep around 10pm and wakes up around 4:30am. “I'm completely awake, and I can't stay in bed,” she says.
Sometimes Amy, a professor of immunology at the University of Colorado, can't fall asleep right away, but she only gets five hours of sleep.
But the surprising thing is that they are usually still active the next day. She walks her dog, works out in the gym for an hour, and after waking up she works out for an hour and a half before eight in the morning.
Her friends are amazed at her ability to accomplish so many tasks despite her lack of sleep, but this is very normal for her family, as her father and brother also do not sleep much.
Most of us, of course, need more time to sleep. The average adult between the ages of 26 and 64 needs between seven and nine hours of sleep every 24 hours, according to the latest review of scientific evidence by the US National Sleep Foundation.
But the huge difference between people in their need for sleep has always been a puzzle. Over the past few years, scientists have succeeded in identifying many genetic factors that play a role in this difference.
From the rare genetic mutations that people like Amy Bernard carry, to hundreds of other more common variants, we see different reasons why some people are able to sleep for very short periods of time without problems.
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These results can be used in the future to protect those suffering from lack of sleep from some common repercussions.
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In 2019, Amy Bernard learned the possible reason behind her miraculous ability to get little sleep.
A research team from the University of California, San Francisco has discovered a genetic mutation associated with sleep duration in humans. Although carriers of this mutation slept at normal times (they did not go to bed early), they woke up very early, often sleeping between four and six and a half hours at night.
The research team discovered that Amy was a carrier of this mutation after analyzing a sample of her blood.
This rare genetic condition is known as familial normal sleep shortening (FNSS). In subsequent years, several other mutations associated with this mutation were identified.
The team's lead researcher, molecular biologist Ying-Hui Fu, says one of the biggest mysteries about familial familial short sleep condition is that people with it appear "healthy" despite their poor sleep. The exact reason behind this is still under investigation.
There is interesting evidence to suggest that genetic variations associated with this functional sleep deficiency syndrome not only cause poor sleep but also protect those affected from the negative effects of poor sleep, including memory impairment, for example.
In a 2019 trial led by Ying-Hui, a genetic mutation associated with familial short sleep syndrome was introduced into mice. The team found that mice carrying a similar mutation not only slept less, but it appeared to protect them from memory loss. Another test also showed that mice carrying some of these mutations were less likely to develop Alzheimer's disease.
In 2014, an international research team conducted a study on non-identical human twins, one of whom carried a genetic mutation that causes poor sleep, and the other of whom did not. They found that the twin carrying the mutation usually slept an hour less than his sibling. They also discovered that when both twins were kept awake for 38 hours straight, the twin with the mutation performed better and had about 40 percent better abilities compared to the other twin.
The researchers also found some interesting differences between the twins' sleep patterns. Although the twin with the genetic mutation slept less, he got about the same amount of non-rapid eye movement (NREM) sleep as his sibling.
Non-rapid eye movement sleep includes deep sleep or slow-wave sleep, and this means that he was, in some way, benefiting more from the sleep he was getting.
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Pharmaceutical dreams
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Despite what has been achieved, research in this field is continuing, which is extremely important, says Ying Hui.
Over the past few years, interest has increased in how we can harness our understanding of these genetic differences in sleep to help people. As for the pharmaceutical industry, hopes are rising to benefit from the results of studying people who suffer from lack of sleep to help develop medications to treat sleep disorders, or even to help military personnel cope with lack of sleep, for example.
Therefore, scientists not only need to clearly understand whether these variables protect those suffering from lack of sleep from negative repercussions, but they also need to know the exact mechanism of action of these variables, because this information may help in producing drugs that do not cause many unexpected side effects.
Ying Hui explains that we must understand how medicine works. She adds, "We don't want to sleep less and then develop Alzheimer's disease, Parkinson's disease, or cancer ten, five, or even twenty years later."
Although the genetic mutations associated with familial short sleep syndrome are one of the most extreme and dramatic examples, they are just a few of the influences that can affect the duration of our sleep.
In general, our sleep duration can be inherited by a rate ranging between 30 and 65 percent, which means that genetic factors play a large role in explaining the reasons for the difference in our sleep duration by a large percentage of up to 65 percent.
To date, hundreds of different parts of the genome that affect sleep duration have been identified. In a new analysis that included data from nearly 650,000 adults, about 244 parts of the genome were found to influence sleep duration. (The research has not been published yet, and is currently in the pre-publication review stage.)
“Taking any of these common mutations on their own, they would only be associated with a difference in sleep duration of about one minute,” says Isabel Austin-Zimmerman, a geneticist at King's College London and lead author on the paper.
But together, these mutations can cause cumulative effects. For the average person, these mutations might reveal genetic differences that cause up to a 20-minute difference in sleep duration between us, says Isabelle.
But so far there isn't much research on which of these common differences can help protect people from the effects of lack of sleep.
However, a recent study led by Chiara Petrocellini, an academic physician specializing in obstetrics and gynecology at University College London, has found evidence of a relationship. The research team studied the genetic makeup of about 343 women with bipolar disorder who had given birth to children.
The women's genes were analyzed to determine their likelihood of suffering from poor sleep, based on the presence of genetic mutations suspected to underlie the condition.
The results revealed that women who were classified as more susceptible to lack of sleep had a reduced risk of developing postpartum psychosis by more than half, compared to other women who were less susceptible to lack of sleep. The results were almost the same for insomnia.
Despite the findings, the researchers recommended further studies, because it is possible that these individuals may have developed a greater tolerance for sleep disturbances earlier in life. This may reduce the impact of sleep disorders on their mood in the postpartum period.
Unfortunately, a genetic predisposition to poor sleep is not always a good thing. In fact, a study by Isabel Austin-Zimmerman and her team in a much larger sample (not necessarily mothers with bipolar disorder) found that genetic variants associated with poor sleep are generally associated with an increased risk of insomnia and feeling tired.
These variables have been linked to several mental and physical health conditions, including attention deficit hyperactivity disorder, depressive symptoms, and type 2 diabetes.
Don't imagine that you are fine
What complicates matters is that those who think that we do not face any problems despite getting a little sleep are not always the best people to assess their situation and the extent of the problems they face.
For example, one study found that when healthy adults' sleep hours were reduced to just four or six hours per night, there was a sustained deterioration in their performance on various cognitive tests.
Despite this decline, participants rated themselves two weeks later, writing only that they felt “slight” sleepiness.
“You become progressively more vulnerable, but you also become less aware of that impairment,” says Hans van Dongen, a sleep scientist at the Center for Sleep and Performance Research at Washington State University, who co-authored the research.
However, many people need less sleep than others. Other research conducted by Van Dongen himself concluded that some people are better able to tolerate sleep deprivation.
But this means that understanding these differences is more complex than simply asking how many hours a person sleeps, or how he feels the next day after waking up.
In the long term, genetic findings, such as those found by Isabelle and Peng Hui, may help identify people who are healthy despite poor sleep. It may also help exclude those who may feel fine, but are still at greater risk of deterioration.
Hopes are rising that these findings will help develop medications that help people with poor sleep improve their ability to cope with it.
But at the same time, these findings can help people understand why they sleep the way they do.
Amy Bernard says knowing she carries a genetic variation of familial sleep deficiency syndrome has relieved her of some stress. As a scientist, she already knew that there were natural differences between humans, including how we sleep.
She also always appreciated the extra time she got from sleeping a few hours to complete her daily tasks, especially while her husband and children were still asleep.
However, Amy wondered whether she was having particularly trouble relaxing, or whether her inability to sleep adequately indicated that she was doing too much.
Finally, Amy Bernard says: “Now I have an answer. I know, genetically, that this is who I am – and I will have to accept it.”
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