image copyrightMaría Medem/BBC
There are people who sleep very little and do not feel any discomfort. But it is not easy to determine whether I am that kind of person.
Amy Pugh Bernard, a professor of immunology at the University of Colorado, says she's always had little sleep for as long as she can remember. Even these days, he usually goes to bed around 10 p.m. and wakes up at 4:30 a.m. “By that time, my mind was so clear that I couldn’t lie down any longer.”
Professor Bernard added that sometimes he can't fall asleep right away and can only sleep for five hours.
What's surprising is that he doesn't feel very tired the next day. I finish walking my dog before 8 a.m., do high-intensity exercise for an hour, and then do work for about an hour and a half. His friends often envy him for being able to handle daily life without sleep, even with little sleep. But this is a common occurrence for Professor Bernard's family. This is because his father and younger brother also feel comfortable with a little sleep.
Of course, most people need more sleep than this. According to the latest research from the National Sleep Foundation, the recommended sleep time for adults ages 26 to 64 is 7 to 9 hours per day.
The reason why each person needs different amounts of sleep has been a mystery that has not been solved for a long time. However, in recent years, scientists have been discovering how genes contribute to this phenomenon. From people with rare genetic mutations like Professor Bernard to people with relatively common genetic mutations, the secret to staying healthy even with less sleep is being revealed little by little. As these studies accumulate in the future, it is expected that it will be useful for those suffering from sleep deprivation.
first clue
In 2019, Professor Bernard discovered a powerful clue that could explain why he stayed healthy even with little sleep.
Researchers at the University of California, San Francisco, have discovered genetic mutations related to human sleep time. People with this genetic mutation have the characteristic of waking up early in the morning and sleeping for only four to six and a half hours a night, even if they go to bed at a normal time. Professor Bernard, who sent blood samples to the research team, also confirmed that he had this mutation.
End of TOP News
This rare trait inherited from parents is called ‘Familial Natural Short-Term Sleep’ (FNSS). In recent years, several additional genetic mutations related to FNSS have been discovered.
Professor Pu Yinghui, a molecular biologist who led the study, said the biggest mystery of FNSS is that "people with this gene sleep less and still maintain their normal state without any problems." Research is still ongoing into the exact cause and process of these characteristics.
What's interesting is that the FNSS gene mutation not only causes short-term sleep, but also protects the body from the side effects of sleep deprivation. Let's take memory decline, a typical side effect of sleep deprivation, as an example.
In a 2019 experiment led by Professor Fu, mice were injected with the FNSS gene mutation. As a result, mice with the mutation not only had reduced sleep time but also did not show any decline in memory. Another experiment found that mice with this mutation were less likely to develop symptoms similar to Alzheimer's disease.
In 2014, a multinational team of researchers studied fraternal twins with a short-term sleep gene mutation in only one side. The researchers confirmed that the group with the mutation slept about one hour less each day than the other group. Additionally, when the two people were prevented from sleeping for 38 hours, the decline in brain function and performance was about 40% lower in the person with the mutation.
The researchers also found interesting differences in the sleep patterns of the two people. Those with the mutation had less total sleep time, but their non-REM sleep time was almost the same as their siblings. Since non-REM sleep includes deep sleep (slow wave sleep), you can get the sleep you need while sleeping less.
Expectations from the pharmaceutical sector
However, Professor Fu says that while research in this field is very important, it is still only just beginning.
In recent years, there has been a growing interest in using these genetic mutations to help people. The pharmaceutical industry hopes that the results of research on short-term sleepers will lead to the development of treatments for sleep disorders in the future or the development of drugs that help people in special occupations, such as soldiers, perform their duties with less sleep.
To achieve this, it is necessary to clearly identify how genetic mutations protect short-term sleepers from the side effects of sleep deprivation, as well as their specific principles and action processes. If this information is lacking, there is a risk of creating drugs that cause unexpected side effects. “You have to fully understand the principle,” Professor Fu said. “No one wants to reduce their sleep time and then develop Alzheimer’s, Parkinson’s disease or cancer 5, 10 or 20 years later.”
image copyrightGetty Images
FNSS-related genetic mutations are a very dramatic and interesting example. However, this is just one of the many factors that determine human sleep time.
Broadly speaking, approximately 30-65% of the difference in sleep time between individuals is explained by genetic factors. Hundreds of genomic regions that affect sleep time have been identified so far. In the latest study that analyzed data from about 650,000 adults, about 244 related gene regions were discovered. (However, this study has only been made public in the form of a preprinted paper that has not yet been officially published.)
Isabel Austin-Zimmerman, a geneticist at King's College London, UK and lead author of the study, explained, "If we look at just one commonly found mutation, the difference in sleep time due to this is only about one minute."
However, when several of these mutations come together, the effect grows like a snowball. Researcher Austin Zimmerman added that even for normal people, their sleep time varies by about 20 minutes depending on which combination of genetic mutations they have.
The problem is that there is still a lack of research identifying which of the commonly discovered genetic mutations prevent the side effects of short sleep.
However, one small clue was discovered in a recent study led by researcher Chiara Petrocelli of the Department of Women's Medicine at University College London, UK. This study analyzed the genetic characteristics of 343 women with bipolar disorder who had given birth.
The researchers calculated their ‘short-term sleep propensity score’ based on the number of genetic mutations related to short-term sleep. The results showed that women with the highest likelihood of short-term sleep had half the risk of developing postpartum mental illness compared to those with the lowest likelihood of short-term sleep. The risk of insomnia was similarly low.
Although further research is needed, the researchers speculated that "it is possible that these women developed a tolerance to sleep disorders earlier as they grew up." This means that this tolerance may have helped women deal with the emotional changes caused by lack of sleep after giving birth.
However, genes that cause you to sleep less are not always good. According to a study conducted by Austin Zimmerman's team on a much wider population than just mothers with bipolar disorder, genetic variants associated with short sleep duration tended to increase insomnia and chronic fatigue. It has also been linked to the risk of several mental and physical diseases, such as attention deficit hyperactivity disorder (ADHD), depression, and type 2 diabetes.
This result does not mean that short-term sleep or related genetic factors themselves directly cause these diseases. However, it shows that even if you have a genetic predisposition to sleep less, you are not always protected from these health risks.
The illusion of ‘it’s okay’
What makes the situation even more complicated is that even people who think they can cope well with little sleep do not know exactly their condition.
According to one study, when healthy adults limited their sleep time to 4 to 6 hours a day, their cognitive ability test scores continued to drop.
But even two weeks after the start of the experiment, participants considered themselves to be just "a little" sleepy.
“As time goes by, the condition continues to worsen, but you do not feel that your performance is declining at all,” said Hans van Dongen, a co-author of the study and professor at the Washington State University Sleep and Performance Research Center.
The amount of sleep each person needs is different. In another study by Professor van Dongen, there were people who showed particularly strong resilience to sleep deprivation. However, this also means that it is difficult to accurately identify individual differences by only asking about sleep time or the individual's subjective mood.
From a long-term perspective, genetic research by researchers such as researcher Austin Zimmerman and Professor Fu is expected to help accurately identify people who actually maintain good health despite sleeping less. Conversely, it can also contribute to finding people who feel fine but are actually harming their health. Furthermore, it may lead to the development of drugs that increase the recovery of people who sleep little.
But right now, it can play a big role in helping people properly understand their sleep characteristics.
Professor Bernard confessed that finding out that he had an FNSS-related gene mutation relieved his emotional burden. As a scientist, he already understood the natural individual differences in humans, including sleep patterns. So, I have always viewed my life positively as I can start my day earlier than others and get work done leisurely while my husband and children are fast asleep.
Nevertheless, Professor Bernard sometimes worried that he was a particularly restless person or that he was having trouble sleeping due to excessive fatigue.
“Now we have a definitive answer,” Professor Bernard said. “I realized that this is who I was born to be, and I decided to accept it as is.”
