For a small number of families, it’s not an alarm clock that regularly wakes them up before sunrise, it’s their genetic make-up, according to a new report in the journal Nature.

In the report, investigators identified a new genetic mutation that causes familial advanced sleep phase syndrome, or FASPS. The mutation alters the functioning of a protein involved in sleep.

These findings may one day help the estimated 0.3 percent of the population with FASPS if investigators find a way to design drugs that modify the activity of the impaired sleep protein, study author Dr. Ying-Hui Fu of the University of California, San Francisco told Reuters Health.

Although many of us would likely love to get a few extra hours of consciousness every morning, FASPS can actually impair people’s ability to function during the day, and they typically nod off by 7:30 pm. Investigators have shown that the condition is essentially a glitch in the body’s biological clock.

These people are not just “early risers,” Fu explained. They often wake up at 1 or 2 in the morning “ready to go,” and there’s nothing they can do about it, she said. “It creates a lot of problems for people, in terms of their marriage,” she said.

During the study, Fu and her colleagues scanned the genes of three generations of a family that had five people who were diagnosed with FASPS. All carried the same mutation.

In a separate experiment, the researchers inserted the same mutation into mice, and they all started waking up earlier.

However, when the researchers inserted the mutation into fruit flies, the flies became night-owls, falling asleep and rising at later hours, suggesting that the biological clocks may differ between mammals and insects.

“This is very significant,” Fu said, because it’s the first study to show that when studying body clocks, results from fruit flies may not always be relevant to humans.

Unfortunately, these findings have little relevance for the millions more people who struggle to fall and stay asleep every night but do not have FASPS, Fu said in an interview. Generally, people with FASPS sleep well every night, she said, but simply have trouble following a normal sleep schedule.

SOURCE: Nature, March 31, 2005.