Gene Cuts Need for Sleep

People With Rare Gene Mutation Refreshed by 6-Hour Sleep

By Daniel J. DeNoon
WebMD Health News

Reviewed By Louise Chang, MD

Aug. 13, 2009 -- At age 69 she's never slept more than six hours a day -- no naps -- yet she's healthy and far more active than most people.

Her 44-year-old daughter also goes to bed at 10 p.m. and gets up at about 4 a.m., even when on vacation. The two share a rare mutation in a gene called DEC2. People with this mutation, researchers find, need less sleep.

The gene is the first ever linked to human sleep behavior. The discovery comes from Ying-Hui Fu, PhD, of the University of California, San Francisco, and colleagues.

"The most interesting thing for me is this genetic mutation can lead to a human behavior trait," Fu tells WebMD. "We cannot blame everything on genetics, but it is obvious our genetic composition affects our behavior. What is involved in regulating our sleep need? This opens the door to start looking at this."

It's a key finding that other researchers have long been trying to find, says Mehdi Tafti, PhD, a geneticist and sleep researcher at the University of Lausanne, Switzerland. Tafti was not involved in the Fu study.

"This is the first time a gene has been found in humans that critically and dramatically controls sleep," Tafti tells WebMD. "We now have evidence that a gene mutation can dramatically change the amount of sleep you get."

Many people set their alarms to go off only six hours after they go to bed. But nearly all of them get some kind of "power nap" during the day to keep them going, says sleep expert Richard Simon Jr., MD, medical director of the Kathryn Severyns Dement Sleep Disorders Center in Walla Walla, Wash.

"Most people who get only six hours' sleep a night finally crash," Simon tells WebMD. "People who really need six hours' sleep and no more are in the minority. Most who get only six hours are going through life exhausted."

Short-Sleep Gene: First of Many to Come?

Although the discovery of the effects of the DEC2 mutation is a major finding, Tafti is quick to note that it affects only one part of the complex sleep process.

"DEC2 is probably a very, very rare mutation. It was found in one family out of 60," he says. "So this mutation explains only some 1% of short sleepers, and we are far from having a complete story."

To prove that the gene affects the need for sleep, Fu and colleagues genetically engineered mice to carry the human DEC2 gene. Sure enough, the mice slept less and stayed awake longer.

When the mice were deprived of sleep, the mutant mice needed less sleep to recover when they finally were allowed to rest.

"These mice just don't need as much sleep," Fu says.

Why? Fu thinks the mutant gene somehow helps mice -- and people -- overcome their sleep need while somehow allowing them to sleep just long enough to stay healthy.

A Drug for Less Sleep?

So what would happen if someone made a drug that did exactly the same thing as the DEC2 mutation?

"If I had a drug that gave a similar effect as DEC2, it is possible it would be pretty safe because the humans who carry it are safe with the mutation," Fu says.

Tafti notes that before anyone tries to make a DEC2-like drug, future research will identify more proteins that affect sleep need.

"Then probably we can act on this pathway and increase sleep or reduce sleep, or make sleep more intense, or improve recovery from sleep deprivation. But that will be for the next decades, not this one," he says.

The Fu study, and an editorial by Tafti and colleague Hyun Hor, MD, appear in the Aug. 14 issue of the journal Science.

SOURCES: He, Y. Science, Aug. 14, 2009; vol 325: pp 866-870. Hor, H. And Tafti, M. Science, Aug. 14, 2009; vol 325: pp 825-826. Ying-Hui Fu, PhD, professor of neurology, University of California San Francisco. Mehdi Tafti, PhD, professor, Center for Integrative Genomics, University of Lausanne; and co-director, sleep laboratory, Vaud University Hospital Center, Lausanne, Switzerland. Richard Simon, Jr, MD, medical director, Kathryn Severyns Dement Sleep Disorders Center, Walla Walla, Wash.

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