Astronauts suffer sleep deficiency in the weeks leading up to and during space flight, says a 10-year-long study.
The study highlights widespread use of sleeping medication use among astronauts.
It recorded more than 4,000 nights of sleep on earth and more than 4,200 nights in space using data from 64 astronauts on 80 shuttle missions and 21 astronauts aboard International Space Station (ISS) missions.
Researchers found that more effective countermeasures to promote sleep during space flight are needed in order to optimise human performance.
"Sleep deficiency is pervasive among crew members. The sleep deficiency has been associated with performance decrements in numerous laboratory and field-based studies," stated Laura K. Barger, an associate physiologist at Brigham and Women's Hospital (BWH) in Boston, Massachusetts.
Despite NASA scheduling 8.5 hours of sleep per night for crew members in space flight, the average (mean) duration of sleep during space flight was just under six (5.96) hours on shuttle missions and just over six hours (6.09) on the ISS missions.
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Twelve percent of sleep episodes on shuttle missions and 24 percent on ISS missions lasted seven hours or more, as compared to 42 percent and 50 percent, respectively, in a post-flight data collection interval when most astronauts slept at home.
The research also highlights widespread use of sleeping medications such as zolpidem and zaleplon during space flight.
Three-quarters of ISS crew members reported taking sleep medication at some point during their time on the space station.
More than three-quarters (78 percent) of shuttle-mission crew members used medication on more than half (52 percent) of nights in space, the study noted.
The other team members in the study were from Harvard Medical School and the University of Colorado.
The study appeared in the journal Lancet Neurology.