No one knows why some lucky folks thrive on five or six hours of sleep per night, while the rest of us suffer if we don't get eight hours of shut-eye. But now scientists have discovered a genetic mutation that could be responsible for the eternal perkiness of short-sleepers.

Combing through a database of sleep-study volunteers, the researchers found two people who needed far less sleep than average. Both had abnormal copies of a gene called DEC2, which is known to affect circadian rhythms and oxygen regulation in mammals. When the scientists bred mice to have the same mutation, the mice slept less and were more active than their regular rodent peers.

So far, the researchers don't know why swapping a single base pair in the DEC2 gene makes mammals need less sleep. But unlike most people who skimp on sleep for long periods of time, subjects with the mutation don't experience the negative health effects of sleep deprivation, such as mood or metabolic changes.

"Finding the mutation is just the first step," said sleep researcher Ying-Hui Fu of the University of California, San Francisco, who co-authored the paper in Science Thursday. "To understand the mechanism is really what's important for us. We want to understand the how, what and why of sleep — how does it affect our health?"

Scientists say the average adult needs eight to 8.5 hours of sleep each night to function optimally, but the short-sleepers reported feeling great on a lifetime average of only 6.25 hours per night. And unlike most of us, who catch up on sleep whenever we take vacation, the mutation carriers stuck to their short sleep schedule even when they had no responsibilities.

But unfortunately for those of us who'd like more time in our day, the short-sleep mutation appears to be very rare. Out of 70 families in the UCSF sleep study database, only one carried the mutation. And Fu said she doesn't know how many people worldwide might be affected.

A commentary about the research, also in Science, calls the discovery "a starting point for studying the regulation of timing and organization of sleep." But because only two people with the mutation have been identified thus far, the authors said the research needs to be replicated in independent studies of other short-sleep individuals.

Fu agrees that more research on the mutation is needed. She's especially interested in understanding how the mutation decreases the need for sleep, and whether it might eventually be used to help others get by on less sleep.

"My fantasy is that as we understand more about how sleep quantitatively affects other health pathways, and we understand more about the mechanism of sleep and how it's regulated in terms of how much we need, someday we'd be able to modulate it in a safe way," Fu said. "So people could sleep less without it affecting their health."

Image: Flickr/supersarasw.

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