Astronauts struggle to get enough sleep – even when special sleep stations have been created, researchers warn today.
Crew members struggle to achieve six hours of sleep a day – and often cut sleep short in advance of missions, researchers warn.
The findings, in The Lancet Neurology, pose questions for ambitions to send humans to Mars and on lengthier space missions.
Researchers found that, on shuttle missions, astronauts struggled to reach six hours a night while on the International Space Station they achieved a little more than six hours.
And they warn about use of sleeping pills – taken by a majority of astronauts at some point.
In space orbit around the earth, the sun rises and sets every 90 minutes – and veteran astronauts recalled problems of light, noise and space-suit cooling systems as all making sleep hard.
Even when sleep stations were installed on the space station, sleep continued to be difficult.
The researchers say it is possible that low gravity may also affect sleep.
The study involved 64 astronauts on 80 shuttle missions and 21 astronauts aboard the International Space Station.
Researcher Dr Charles Czeisler, of Brigham and Women’s Hospital, Boston, USA, said: "Future exploration spaceflight missions to the moon, Mars, or beyond will require more effective countermeasures to optimise human performance by promoting sleep during spaceflight.
"These may include modifications to schedules, strategically timed exposure to specific wavelengths of light, and behavioural strategies to ensure adequate sleep, which is essential for maintaining health, performance and safety."
Writing in the journal, Dr Mathias Basner, from the University of Pennsylvania, USA, says: "Only four people have consecutively lived and worked for more than 1 year in space; as such, how sleep and behavioural health will be affected during space exploration is poorly understood.
"Studies of the physiology of sleep stages and the intensity of sleep…in space are necessary to answer the important question of whether spaceflight reduces the need for sleep and therefore the ability to sleep, or whether it reduces the ability to sleep but not the need for sleep."
Prevalence of sleep deficiency and use of hypnotic drugs in astronauts before, during, and after spaceflight: an observational study. The Lancet Neurology 7 August 2014 [abstract]
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