A mutant gene behind an “early bird” sleep disorder has been identified by U.S. researchers.People with this “time-shift” trait -- called familial advanced sleep phase syndrome (FASPS) -- consistently fall asleep at an early hour and then wake up well before dawn.An estimated 0.3 percent of humans have FASPS, according to the researchers. They don’t necessarily get less sleep than other people, but they do sleep on a different schedule than most of the rest of us. Some people with FASPS adjust to this time-shift, while others are bothered by being out of sync with those around themLooking into the problem, researchers at the Howard Hughes Medical Institute and the University of California, San Francisco studied a family strongly affected by FASPS. They discovered that the mutation responsible for FASPS lies in a gene with no previous connection to circadian rhythm.It isn’t yet clear exactly how this mutant gene affects a person’s sleep cycle, since it appears to act differently in different species. For example, in fruit flies the mutant gene lengthens circadian rhythm, while it shortens it in mice and humans, the researchers said.
