91av

STOPPING astronauts from nodding off could be a major problem on long space
flights, especially any mission involving time in orbit. The bizarre light-dark
cycle in space can make the body’s internal clock break down, and what happened
to Jerry Linenger on board the Russian Mir space station shows just how bad the
effect can be.

Linenger lived on Mir for 5 months in 1997. He tried to keep strict sleeping
hours, but the reduced power on the ageing space station meant that the lights
were dimmer than in most offices. The strongest light cues came from sunlight
streaming in through the windows. Light and dark alternated as Mir orbited the
Earth every 90-odd minutes, and it played havoc with Linenger’s sleep
patterns.

“Day, night, day, night, 15 times a day starts messing you up after a while,”
he says. “At the 4-month point I lost it.” For two Russian colleagues who were
less methodical about their sleeping hours it was even worse. “They’d nod off
and float right past you,” he recalls.

Timothy Monk at the University of Pittsburgh Medical Center studied data on
Linenger’s sleep quality, body temperature and performance in psychological
tests. He found that after around 90 days the astronaut’s sleep quality
deteriorated rapidly.

Monk thinks the unnatural day-night cycle combined with lack of exercise
affects a region of the brain called the endogenous circadian pacemaker, which
controls the body’s daily rhythms. Finding ways to keep the ECP on track will be
vital to the success of future long-haul missions, he says.