The Science Behind Why Some People Only Need 4 Hours of Sleep per Day

Are you one of the lucky people with a rare gene that allows you to sleep only four hours per night and still feel refreshed?
people sleep

Sleep governs our neurological and cognitive functions, like moving, thinking, learning, memory, and feeling energetic. While many people can sleep as much as six, seven, or eight hours daily, some find it incredibly difficult. This is the case of Mr. Brad Johnson.

Johnson, 65, initially assumed that his inability to sleep as much as other people meant he had a medical condition. He carried this anxiety in his mind despite being a focused and energetic child and then a high-achieving adult. Mr. Brad said in a statement to Popular Mechanics, “I just physically cannot sleep like others. And everything you read says you’d need to have seven, eight, nine hours of sleep a night. Otherwise, you’ll have major health problems and won’t be able to be as productive.”

He never slept beyond six hours per night

Mr. Johnson has only slept four to six hours a night for as long as he can remember. His father and four of his seven siblings were aboard the same boat. For them, sleeping for six hours is similar to sleeping for eight or nine hours for most people. “If I have less than four hours of sleep per night, I’ll have the same problem as everyone else who is sleep-deprived,” he explained.


Johnson excelled in college, rising to leadership positions, and having eight children with his wife. Despite his hectic schedule, he questioned why he felt so well after only six hours of sleep – and why he never required an alarm clock to wake up and feel refreshed every morning.

Why did Mr. Johnson feel great on very little sleep?

Johnson didn’t start looking for answers to his sleeping problems until 2005. He enrolled in a sleep study group to find people who function effectively with very little sleep. A few years later, he underwent a follow-up sleep study after his blood revealed specific gene mutations that most individuals don’t have. During the studies, Johnson completed thorough questionnaires on his sleep patterns and health during the research, and researchers tracked his daily sleep and activity levels for eight days.

Ying-Hui Fu from the University of California, San Francisco’s Weill Institute for Neurosciences, investigates sleep behaviors and circadian rhythms, the body’s natural clock for sleeping. In 2009, she and her colleagues discovered that particular mutations in the DNA of so-called “short sleepers” are responsible for super-efficient sleep. Her research had found five mutations in three genes that influence how much sleep people require at this time, but Fu believes there are additional genes involved.

1024px University of California Santa Barbara Entrance
University of California by UCSB-IGSA under CC BY-SA 4.0

“Short sleepers”

Sleeping for a long period does not always imply good quality sleep. However, the more effective our sleep is, the less we require. Short sleepers are known for this trait.

“Short sleepers only need approximately half as much sleep as the great majority but perform as well as normal sleepers,” Fu told Popular Mechanics.

While it’s an uncommon person who is genetically programmed to sleep for fewer hours per day, all of the people Fu and her team have identified as short sleepers share key characteristics: They tend to live healthier and longer, both mentally and physically.


Short sleepers have gene mutations

Following this revelation, Fu and her team began looking for people who fit the profile of sleeping late and rising early. “We received thousands of emails from people saying, ‘I’m like that,’ or ‘I know someone like that,” Fu says. While many people in the group slept less, just about 100 people, including Johnson—emerged as real short sleepers.

shutterstock 1946049973

After confirming that the common gene mutation impacted all short sleepers, the researchers wanted to know how it affected the brain. They turned to mice to acquire a deeper knowledge of the brain neurocircuitry involved in sleep. “Mice with the same mutation are sleepless as well, and we believe this is real,” Fu says.

Fu examined the brains of mice with short-sleep gene mutations, searching for “distinct neuro-circuits for efficiency and sleep duration” and specific patterns of brain activity during sleep. While she found some universal brain pathways, she believes more research is needed to understand how genes affect human brain function. But seeing the identical gene mutations and behaviors in healthy mice supported her claim that people may sleep four to six hours and still be healthy and function correctly.


How does It feel to be a “short sleeper”?

The research finds that short sleepers are truly lucky since they seem to share some excellent characteristics:

  • More active
active senior man

“Short sleepers sleep less and are more active while awake – roughly 18 to 20 hours – than usual sleepers.” “They have so much extra time so they can multitask,” Fu explained.

  • Fewer diseases

Compared to regular sleepers, short sleepers appear to have fewer ailments. Heart disease, diabetes, and other disorders do not manifest themselves until much later in life. Even the sleepers in Fu’s studies who are 60 to 80 years old remain active and healthy. For instance, one study participant who’s almost 80 years old was recently training for a triathlon. They can deal with stress better than regular sleepers: they are “very optimistic, cheerful, and resilient,” she says.

  • Pain tolerance is higher than usual.

“Short sleepers also have some unusual features, such a higher pain tolerance,” she adds. A higher-than-normal pain tolerance, in particular, is a prevalent symptom of short sleepers. Johnson has firsthand knowledge of this topic. He needs both knees replaced, but they don’t affect him unless he leaps or runs, so he’s postponed the surgery. “It was inconvenient. It was excruciatingly painful.” He explains, “But it was something I could accomplish.”

  • Other unusual traits

Fu explains, “one of the research volunteers had a remarkable memory and never needed to take notes in class.” Another can communicate in 13 different languages. Others can work out for lengthy periods without experiencing pain. According to Fu, since a hereditary component is a significant aspect of sleep behavior, it’s not surprising that Johnson and some of his near family members have the same short sleep needs. Nonetheless, she claims that it looks to be a rare trait. None of Johnson’s children, and most of his siblings’ children, are short sleepers.

Johnson considers his short-sleep genes a blessing, which is why he has accomplished far more than he would have otherwise, including giving back to those in need through his church, he claims. “I believe that giving back and assisting others brings us enormous joy and contentment in life.”


Why do people have this mutation?

Fu isn’t sure, but she thinks it has something to do with the fact that there have been more hours of bright light with the introduction of electric lights in the home. Maybe it’s a reaction to going to bed later in the evening. It’s interesting to guess, but she admits there’s no way to prove it right now.

Future studies

The most vital thing is to plan for more studies to understand what short sleepers’ brains do during sleep. For instance, is there anything different about their REM cycles? Fu hopes that this knowledge will lead to therapies to help everyone have better sleep and live healthier, longer lives.