WASHINGTON -- A sleep syndrome that sends people early to bed and early to rise doesn't necessarily make them healthy, wealthy and wise. The disorder, traced to a single gene, can send sufferers to bed when everybody else is still going strong, researchers at the University of Utah have found.
Understanding what governs people's wake-sleep cycles has important medical implications for dealing with insomnia, jet lag, shift work and depression, the scientists report in the September issue of the journal Nature Medicine.
Researchers studied people who have a shorter than normal wake-sleep cycle. Regardless of work schedules or social pressures, these folks just can't stay up much later than 8:30 p.m. and they tend to wake up around 5:30 a.m.
It's called "familial advanced sleep-phase syndrome" because it shifts the normal wake and sleep pattern forward by three to four hours.
Louis Ptacek and colleagues found 29 people in three families with the disorder. One family included a grandmother, daughter and grandchild all with the same sleep disturbance.
The normal population contains plenty of "morning lark" and "night owl" people who function better at different times of day, but people with this syndrome are not simply morning people, Ptacek emphasized.
Most creatures seem to operate on a biological clock approximately synchronized to a 24-hour day. This rhythm controls a variety of daily biochemical and behavioral cycles including fluctuations in sleep and wakefulness.
For people with this syndrome the cycle is shorter and the constant conflict between their body clock and coping with the rest of the world leads to their shifted sleep-wake rhythm.
"These aren't diseases per se, and most people just live with this sleep pattern and never see a doctor about it," Ptacek said. Some cope with it fairly well, but it can be disabling for others.
By studying the family relationships the scientists found that the disorder is inherited in a way common to other inherited traits caused by a single gene, such as eye color.
So now Ptacek's team is working to identify the specific gene responsible. Finding the gene could lead them to the protein it produces to cause the body's time shift -- a discovery that could then lead to the development of drugs to treat not only the sleep disorder, but jet lag and other conditions.
But, said Ptacek, "we need to understand the normal biology first. Then we can work on altering the clock and helping people who fly or do shift work."
"Presumably, this protein is just one of the gears in the (body) clock. By studying one gear we can get a handle on the other gears around it and we may get an insight about why they have this trait and how the normal clock functions," he said in a telephone interview.
The search for the gene may be arduous.
"There are approximately 80,000 genes in human genome, this is a single one of those 80,000. Think of the genome as a library with 80,000 books and we're looking for a spelling error in a single book," he said.
His report was greeted with enthusiasm.
"I think this is a really exciting finding," said David Earnest of Texas A&M University, who studies the cell biology of the circadian clock that regulates sleep and wake patterns.
"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," Earnest said in a telephone interview.
What researchers have been looking for in humans is either a disease or mutation that is directly associated with a variant circadian rhythm, he explained. They want to learn how that affects mental health and to understand its role in problems such as jet lag and seasonal affective disorder -- better known as winter blues -- which is common in northern areas.
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