Scientists uncover genetic secret behind people who thrive on just 4 hours of sleep

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Most healthy adults need seven to nine hours of sleep a night to maintain good health. However, some people function normally on just four to six hours. Scientists say rare genetic mutations may explain why.

Aimee Pugh Bernard, an immunology professor at the University of Colorado in the United States, is one such person. She typically goes to bed around 10pm and wakes up at 4:30am.

Even when she falls asleep later than usual and gets less than five hours of rest, she feels refreshed the following day. She walks her dog, exercises for an hour and completes an hour and a half of work before 8am.

In 2019, Bernard discovered that her ability to function on limited sleep was linked to a rare genetic mutation. Researchers at the University of California, San Francisco, identified a genetic variant associated with naturally shorter sleep duration.

People carrying these mutations generally go to bed at normal times but wake up early, sleeping between four and six and a half hours without experiencing the usual effects of sleep deprivation.

The inherited condition is known as Familial Natural Short Sleep (FNSS). Researchers have since identified several other genetic mutations associated with the trait.

Scientists believe these mutations may not only reduce the amount of sleep needed but also protect the brain against some harmful effects of sleep deprivation.

In a 2019 experiment, researchers introduced FNSS-associated genetic mutations into mice and found that they experienced less memory impairment despite sleeping for shorter periods.

Another experiment suggested that some of these genetic changes could also reduce the risk of diseases such as Alzheimer's.

A 2014 study involving twin brothers provided further evidence. One brother carried a genetic mutation associated with short sleep, while the other did not. The mutation carrier regularly slept about an hour less than his brother.

During an experiment involving 38 hours of continuous sleep deprivation, the decline in his work performance was about 40 percent smaller than that of his brother.

Researchers estimate that total sleep duration is 30 to 65 percent heritable, meaning genetic factors account for a substantial proportion of differences in how long people sleep.

A recent study analysing data from around 650,000 people identified approximately 244 genetic regions associated with sleep duration. The findings have not yet been published.

However, scientists caution that believing oneself capable of functioning on little sleep does not necessarily mean the body is getting enough rest.

Studies involving healthy adults restricted to four to six hours of sleep a night for two consecutive weeks found a steady decline in performance on cognitive tests. Despite this, participants reported only a slight increase in fatigue.

Researchers say studying the genetic traits behind naturally short sleep could provide important insights into the long-term effects of sleep deprivation.

The findings may eventually help scientists develop treatments for sleep disorders and reduce the harmful effects of insufficient sleep. However, further research is needed to understand how the genetic mutations work.

Source: BBC