Researchers have found a genetic mutation in two people who need far less sleep than average, a discovery that might open the door to understanding human sleep patterns and lead to treatments for insomnia and other sleep disorders.

The finding, published in the Friday issue of the journal Science, marks the first time scientists have identified a genetic mutation that relates to sleep duration in any animal or human.

Although the mutation has been identified in only two people, the power of the research stems from the fact that the shortened sleep effect was replicated in mouse and fruit-fly studies. As a result, the research now gives scientists a clearer sense of where to look for genetic traits linked to sleep patterns.

“I think it’s really a landmark study,” said Dr. Charles A. Czeisler, a leading sleep researcher and chief of sleep medicine at Brigham and Women’s Hospital in Boston. “It opens up a window to the understanding of the genetic basis of individual differences in sleep duration. Now you have a piece of the puzzle and you can begin to try to trace back as opposed to having little information as to where to start.”

The gene mutation was found by scientists at the University of California, San Francisco, who were conducting DNA screening on several hundred blood samples from people who had taken part in sleep studies.

The scientists were searching the samples for variations in several genes thought to be related to the sleep cycle. In what amounts to finding a needle in a haystack, they spotted two DNA samples with abnormal copies of a gene called DEC2, which is known to affect circadian rhythms. They then worked back to find out who provided the samples and found a mother and daughter who were naturally short sleepers. The women routinely function on about six hours of sleep a night; the average person needs eight hours to eight and a half hours of sleep. When scientists bred mice with the same mutation, the animals slept less and recovered quicker from periods of sleep deprivation compared with regular mice.

“We know sleep is necessary for life, but we know so little about sleep,” says Ying-Hui Fu, study co-author and professor of neurology at the University of California, San Francisco.

What distinguishes the two women in the study and other naturally short sleepers is that they go to bed at a normal time and wake up early without an alarm. The two women, one in her 70s and the other in her 40s, go to bed around 10 or 10.30 at night and wake up alert and energised around four or 4.30 the morning, said Professor Fu.

While many people might sleep only six or fewer hours a night, most were not naturally short sleepers. For instance, they use stimulants and alarm clocks to maintain a shortened sleep schedule. The real benefit of the research will come if and when the mutation is identified in other individuals. That could lead to new discoveries about sleep timing and duration, and possibly new treatments for sleep disorders. — © 2009 The New York Times News Service

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