Tuesday, August 31, 1999 Published at 08:24 GMT 09:24 UK
Sleep research could combat jet lag
People with the disorder fall asleep early and can't sleep in
Scientists have discovered a genetic disorder which they say is responsible for people who find it impossible to stay up late or sleep in.
The findings could lead to new treatments for jet lag, insomnia and seasonal depression.
This means the person's body clock is three to four hours faster than normal.
Writing in Nature Medicine, the scientists, led by Dr Louis Ptacek, say they found 29 people in three families who suffered from the disorder.
In one family, a grandmother, daughter and grandchild all had the disorder which is not the same as simply finding it difficult to stay in bed in the morning.
Dr Ptacek said most people with the disorder do not see their doctor about it, but some find it causes them problems.
Scientists hope that by studying the syndrome they may be able to identify the gene responsible.
This could lead them to the protein it produces to cause the shortened time clock which, in turn, could be used to formulate new drugs to treat jet lag and other conditions.
However, they admit that it will take some time to isolate the gene.
Dr Ptacek compared the task to "looking for a spelling error in a single book "in a library full of 80,000 books.
Experts in circadian rhythms - the rhythms that regulate sleep and wakefulness - say the research is exciting.
David Earnest of Texas A&M University said: "This is the first time that anyone has identified a genetically inherited trait that involves the expression and control of the circadian rhythm in humans. That's really critical."
He added that finding the key to different patterns of circadian rhythm could help researchers to discover their role in jet lag, seasonal affective disorder and other mental health problems.