Scientists have good and bad news for hard-driving individuals who boast they only need six hours of sleep a night.
The good news is that researchers at the University of California-San Francisco have identified a family with a genetic mutation that causes members to require only six hours of sleep a night. They even managed to create mice and fruit flies with a similar mutation who also had short sleep cycles.
The bad news? The gene is vanishingly rare in humans, occurring in less than 3% of people.
So almost everyone who claims they only need six hours' sleep is kidding themselves. And the consequences of chronic sleep deprivation are serious, says Clete Kushida, president of the American Academy of Sleep Medicine and director of Stanford University's Sleep Medicine Center. Sleep deprivation has been linked to an increase in motor vehicle accidents, deficiencies in short-term memory, focus and attention as well as depressed mood and a decrease in the ability to control appetite.
The family with the gene mutation, a mother and daughter, were discovered by researchers at UCSF who were studying circadian rhythms, the waxing and waning biochemical cycles that govern sleep, hunger and activity.
A recent study on people who naturally go to sleep and get up very early turned up the women, who had a very different sleep pattern — neither needed more than six to 6½ hours of sleep a night and both were well-rested, healthy and energetic.
"One of them is over 70, always traveling internationally and extremely active. She dances three or four nights a week," says Ying-Hui Fu, a professor of neurology at UCSF.
When the scientists looked at the pair's DNA, they found a tiny mutation in a gene called DEC2, which governs cell production and circadian rhythm, among other things.
The mutation seems to result in people who are natural short sleepers, needing much less than the normal eight to 8½ that most humans require for well-rested functioning, according to their paper, published in the Aug. 14 edition of the journal Science. Fu and her colleagues were able to genetically engineer both fruit flies and mice to have the same mutation and have been researching its causes and effects. It appears humans and mice that carry the mutation get more intense sleep, as measured by slow-wave electrical activity in the brain, and so need less of it.
But Fu estimates that only about 3% of the population is likely to have this gene and cautions that most people who habitually get less than eight hours sleep a night are only building up a large, dangerous, sleep debt.
Fu says her lab is investigating whether it might be possible to mimic the effects of the gene with therapeutic compounds, but cautions the research is only at the very beginning. For now, the only real answer to true productivity is to sleep as much as your body needs, she says.
"For years when I was younger and a student I drank tea and coffee, I did everything possible to only sleep six hours. But now, since I studied this, I know it's not good for my health so I sleep eight hours a night," she says.
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