Can genetics explain why some people thrive on less sleep?
(Illustration by Christopher Cherrington | The Salt Lake Tribune) Utah researchers are trying to determine if genetics can explain why some people thrive on less sleep.
For as long as Brad Johnson can remember, he has never been able to sleep more than six hours a night. Most nights, he sleeps even less. Johnson, 63, always wakes without an alarm clock, feeling rested and ready for the day.
“If you paid me $100,000 to sleep eight hours tonight, I couldn’t do it,” he said.
He’s not the only one in his family like this. Two of his seven siblings also are natural short sleepers. He suspects that their father was one, too.
At least 15 years ago, he said, one of his brothers reached out to a sleep doctor at the University of Utah, who took an interest in the family, collecting blood samples and conducting interviews at a reunion. Ultimately, researchers identified six members of Johnson’s extended family, men and women, who get by on an average of less than six hours of sleep a night, much less than the 8 1/2 hours that people typically need to function at their best.
Researchers wondered whether there was something about their genetics that might help explain how sleep works for the rest of us.
“The problem is, we know so little about what sleep really is and what it’s for,” said Louis Ptacek, a neurologist at the University of California, San Francisco. “As we identify more and more genes, hopefully this will outline a system, or systems, that are critically important to sleep.”
Ptacek and his colleagues identified a gene mutation that shows up in every naturally short-sleeping member of Johnson’s family. When the scientists took the mutated version of the gene and put it in lab mice, they found that the mice needed about an hour less sleep a day than their siblings that did not have the gene.
The researchers, who published their findings in the journal Neuron on Wednesday, determined that the gene, ADRB1, has a direct bearing on how much sleep people need. Their findings, they said, could be used to design therapies to help people with sleep problems.
The study is the second to identify a genetic explanation for why some people thrive on less sleep. Ying-Hui Fu, a neuroscientist at the University of California, San Francisco, who is married to Ptacek, led a team that found the first one a decade ago. She also worked on this new study.
The gene that Johnson shares with his short-sleeping siblings affects communication among certain brain cells. From studies conducted with lab animals, scientists already knew that these exchanges are important to sleep regulation. However, it was helpful to see that when the system is naturally altered in humans, it results in people with real differences in their sleep needs.
“It was predicted from animal studies, but actually having people who have changes as a result of it is really important,” said Amita Sehgal, a neuroscientist at the University of Pennsylvania who studies sleep using fruit flies and was not involved in the study led by Fu and Ptacek.
The specific gene that the short-sleeping members of Johnson’s family carry shows up in about 1 in every 25,000 people. But there are other genes that make people less likely to need eight or more hours of sleep. There is the gene Fu found a decade ago, for example. She said she has since found a few more that she has yet to describe in peer-reviewed journals. Overall, however, scientists do not know how widespread natural short-sleeping is. Ptacek guessed that it is “not rare, but not super common, either.”
Fu’s goal is to find 10 short-sleeping genes and to learn if there are any connections among them. For now, the new gene and the one she discovered in 2009 do not appear to be related.
The team is also interested in the personality traits they have observed among the short-sleeping families they have studied. The scientists don’t have enough data yet to know if these traits are associated with needing less sleep, but informally, Ptacek and Fu said they have found natural short-sleepers to be optimistic and driven, and resilient against stress and pain.
Could Johnson’s short sleep explain his full and accomplished life? He enjoys hiking, biking and rock climbing. He runs marathons. He was the chief financial officer for outdoor sports gear company REI in Washington state until he retired in 2009 and moved back to Utah, where his family is from.
He said that he has used the two or three extra hours of waking time he gets each day to read, work and spend time with his eight children.
“It gave me additional time with my children,” he said. “I would consider it a great blessing in my life.”