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In an extensive study of sleep monitoring and sleeping pill use in astronauts, researchers from BWH's Division of Sleep and Circadian Disorders, Harvard Medical School and the University of Colorado found that astronauts suffer considerable sleep deficiency in the weeks leading up to and during spaceflight. The research also highlights widespread use of sleeping medication among astronauts. The study, published in The Lancet Neurology this month, 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 is the largest study of sleep during spaceflight ever conducted and concludes that more effective countermeasures to promote sleep during spaceflight are needed in order to optimize human performance. "Sleep deficiency is pervasive among crew members," said Laura Barger, PhD, associate physiologist in the BWH Division of Sleep and Circadian Disorders, and lead study author. "It's clear that more effective measures are needed to promote adequate sleep among crew members, both during training and spaceflight. Although we didn't have the opportunity to evaluate performance during spaceflight, sleep deficiency of this magnitude has been associated with performance reductions in numerous laboratory and field-based studies."Despite NASA scheduling 8.5 hours of sleep per night for crew members in spaceflight, the average duration of sleep was just under six hours on shuttle missions and just over six hours on ISS missions. 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.
Moreover, the results suggest that astronauts' build-up of sleep deficiency began long before launch, as they averaged fewer than 6.5 hours of sleep per night during the training interval occurring approximately three months prior to spaceflight. The research also highlights widespread use of sleeping medications such as zolpidem and zaleplon during spaceflight. 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 of shuttle-mission crew members used medication on more than half of nights in space."The ability for a crew member to optimally perform if awakened from sleep by an emergency alarm may be jeopardized by the use of sleep-promoting pharmaceuticals," said Barger. "This consideration is especially important because all crew members on a given mission may be under the influence of a sleep-promoting medication at the same time." Charles Czeisler, PhD, MD, FRCP, chief of the Division of Sleep and Circadian Disorders, and senior study author, added: "Future exploration spaceflight missions to the moon, Mars or beyond will require development of more effective countermeasures to promote sleep during spaceflight in order to optimize human performance. These measures may include scheduling modifications, strategically timed exposure to specific wavelengths of light and behavioral strategies to ensure adequate sleep, which is essential for maintaining health, performance and safety."