MOONSLEEPING BAD FOR SPACEWALKING

By Laura SandersWeb edition : Monday, November 17th, 2008

Day three of the Society for Neuroscience annual meeting offered news about Down syndrome and sleep cycles

Melatonin by moonlight

Moonlight may interrupt astronauts' sleep cycles by messing with their melatonin, a new study shows. Sleep cycles are regulated by the type and amount of light that people encounter. When a person goes to sleep, the hormone melatonin circulates through the body to maintain a drowsy state. But if a light comes on, the body's melatonin levels drop, causing the person to wake up.

Astronauts are notoriously bad sleepers, says Benjamin Warfield of Thomas Jefferson University in Philadelphia. They average just four to six hours of sleep a night when they're on a mission and amass a huge sleep deficit. But no one knew how moonlight might be affecting this chronic lack of sleep.

To figure it out, the researchers built a piece of equipment they call the Moonlight Machine — a complicated series of lights, mirrors, lenses, and filters — to mimic light conditions on the moon. Subjects sat inside the Moonlight Machine between 2 and 3:30 a.m., a time when melatonin levels in the body are normally high. The researchers found that melatonin levels were diminished after moonlight exposure. The team's next step is to repeat the experiments at all points during the night. Ultimately, Warfield would like to design visors and window blocks that could regulate the amount of moonlight for astronauts. "We're really excited to see where this goes," says Warfield. The team plans to begin studying how the lighting conditions on Mars might affect the human sleep cycle.

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