Astronauts typically spend six months on the International Space Station, but since longer missions are planned, researchers want to learn more about what happens to sleep when humans endure in space. (NASA)
Astronauts commonly suffer from a poor night's sleep before and during their spaceflights, when use of sleep medications is widespread, researchers have found.
Space is a hostile environment. What's more, the isolated and confined sleeping quarters are noisy and physically uncomfortable, with light-dark cycles that don't correspond to Earth's 24 hour day.
Since American astronauts Neil Armstrong and Buzz Aldrin both reportedly had trouble sleeping after landing on the moon in 1969, NASA has looked for ways to improve sleep conditions in space. The agency schedules 8.5 hours of sleep per night for crew members.
In Thursday's online issue of the journal Lancet Neurology, U.S. researchers studied the sleep patterns of 64 astronauts on shuttle missions and 21 astronauts aboard International Space Station missions before, during, and after their spaceflight — more than 4,000 nights of sleep on Earth and more than 4,200 in space .
"We report results of the most extensive study of sleep during spaceflight done to date," Laura Barger from Harvard Medical School in Boston and her co-authors say.
"Our findings show that sleep deficiency in astronauts was prevalent not only during space shuttle and International Space Station missions, but also during a 90-day preflight training interval. Furthermore, use of sleeping drugs was pervasive during spaceflight. Because chronic sleep loss leads to impaired performance, our findings emphasize the need for development of countermeasures to promote sleep during spaceflight."
Astronauts reported using sleep medications, mostly zolpidem (sold in Canada as Sublinox and in the U.S. as Ambien), on 52 per cent of nights during shuttle missions.
But there's only "marginal benefits for sleep duration, efficiency and quality" with the drugs, sleep specialists Mathias Basner and David Dinges from the University of Pennsylvania in Philadelphia say in a journal commentary published with the study.
The U.S. Food and Drug Administration has cautioned that people using sleeping pills "should be cautioned against engaging in hazardous occupations requiring complete mental alertness or motor co-ordination," Barger's team noted.
In the study, journals from space station astronauts included comments such as:
- "I found myself getting pretty inefficient; by the time I go to bed tonight my work day will have been about 27 hours, and that's on top of two nights with pretty minimal sleep."
- "Very tired. Woke up at 2 am and couldn't get back to sleep. Finally fell asleep and overslept."
The commentary article describes some of the factors that can harm sleep in space, such as how microgravity forces astronauts to sleep in bags tethered to a wall, which can lead to back pain and fluid shifts.
The pair of authors say space exploration, such as to Mars, requires that scientists answer the fundamental question of what happens to our sleep and biological functions when we stay in space for prolonged periods.
The study's researchers weren't able to directly measure sleep stages to look for differences associated with sleeping pills or to objectively measure cognitive performance or errors.
NASA funded the study. Participants included all non-Russian crew members assigned to shuttle flights with in-flight experiments from 2001 to 2011 or space station expeditions from 2006 to 2011.
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