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 warned 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.
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.
Fatigued space walk
Former Canadian astronaut Dr. Dave Williams was one of the participants, and calls it an important study. During his second flight, Williams recalls he was asleep in the air lock preparing to do a spacewalk when he and a U.S. astronaut were aroused by an alarm.
"I had practised doing spacewalks with little sleep just in case. Sometimes it's very important to focus despite the fatigue."
Williams said you can tell if an astronaut is truly sleeping while floating in space because his or her arms float up by the face. Once he even dreamed someone reached out to grab him before he realized the arms were his own.
In the medical world, Williams said, the effects of fatigue are often compared with those of low levels of oxygen.
"A good example would be if you were to fly to any city at a higher elevation, you get out of the airplane and you feel fine. But then try and run and then you notice it. Fatigue is sort of the same."
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. For example, microgravity itself could influence sleep.
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.