JOIN USAstronauts suffer considerable sleep deficiency during space flight and rely on sleeping pills to doze off, scientists have found.
Researchers from Brigham and Women's Hospital (BWH) Division of Sleep and Circadian Disorders, Harvard Medical School, and the University of Colorado conducted an extensive study of sleep monitoring and sleeping pill use in astronauts.
The study 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.
The 10-year study, the largest study of sleep during space flight ever conducted, concluded 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," said Laura K Barger, associate physiologist in the BWH Division of Sleep and Circadian Disorders and lead author of the study.
"It's clear that more effective measures are needed to promote adequate sleep in crew members, both during training and space flight, as sleep deficiency has been associated with performance decrements in numerous laboratory and field-based studies," said Barger.
Despite NASA scheduling 8.5 hours of sleep per night for crew members in space flight, the average duration of sleep during space flight was just under six hours on shuttle missions, and just over six hours on ISS missions.
Twelve per cent of sleep episodes on shuttle missions and 24 per cent on ISS missions lasted seven hours or more, as compared to 42 per cent and 50 per cent, respectively, in a post-flight data collection interval when most astronauts slept at home.
The results suggest that astronauts' build-up of sleep deficiency began long before launch, as they averaged less than 6.5 hours sleep per night during the training interval occurring approximately three months prior to space flight.
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, and more than three-quarters (78 per cent) of shuttle-mission crew members used medication on more than half (52 per cent) of nights in space.
"The ability for a crew member to optimally perform if awakened from sleep by an emergency alarm may be jeopardised by the use of sleep-promoting pharmaceuticals," said Barger.
"Routine use of such medications by crew members operating spacecraft are of particular concern, given the US Federal Drug Administration (FDA) warning that patients using sleeping pills should be cautioned against engaging in hazardous occupations requiring complete mental alertness or motor coordination, including potential impairment of performance of such activities that may occur the day following ingestion of sedative/hypnotics," Barger said. The study is published in The Lancet Neurology journal.