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Monday, May 14, 2007

Bright lights, big sleep for Mars -- and Earth, too

Two bursts of bright light in the evening help the brain's clock adapt to a longer day, sleep researchers at Brigham and Women's Hospital report, something important for astronauts traveling to Mars but also for earthbound travelers, shift workers or other people whose internal clocks are out of synch.

"Utilization of bright-light exposure could work whether you're going to Mars or Los Angeles," Dr. Charles Czeisler, chief of sleep medicine at Brigham and Women's Hospital, said in an interview.

Czeisler, Dr. Richard E. Kronauer of Harvard and colleagues from the University of Lyon and the University of Colorado conducted a study for NASA's National Space Biomedical Research Institute that appears in today's Proceedings of the National Academy of Sciences.

They set out to solve the problem of what could be perpetual jet lag-like fatigue on an eventual year-and-a-half-long mission to Mars, a plan announced by President Bush in 2004. The Martian day is 39 minutes and 35 seconds longer than a day on Earth -- which doesn't seem like much at first, but adds up to more than four hours in just one week.

The researchers sequestered 12 healthy people in rooms with no time cues for 65 days. First they observed their individual internal clocks, finding a range of differences in the timing of when their bodies released melatonin. Some people were releasing the sleep-promoting hormone as much as five hours before bedtime while for others it was an hour ahead.

"This may explain why some individuals feel so tired in the evening," Czeisler said. "It's as if people are in different time zones, like England and Boston. Their internal clocks are spread out over many time zones.

Over the next 30 days, the participants were exposed to a longer day under varying amounts of light. Those who got two 45-minute sessions of bright light in the evening were able to adapt their sleep/wake cycles to a longer-than-24-hour day.

"These results suggest that people could be treated for sleep disorders" in this way, Czeisler said.

Posted by Elizabeth Cooney at 05:00 PM
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