A 10-year study of sleep patterns during space flight has revealed lack of adequate sleep -- and use of sleeping pills -- is widespread among astronauts in the United States space program.

Researchers from the Division of Sleep and Circadian Disorders at Boston's Brigham and Women's Hospital, Harvard Medical School and the University of Colorado found that astronauts with the National Aeronautics and Space Administration not only suffer considerable sleep deficiency in the weeks leading up to and during space flight, but also use sleeping medication regularly and extensively, explained a news release.

The concerning findings, published in the Aug. 8 edition of The Lancet Neurology, included documentation of more than 4,000 nights of sleep on Earth and more than 4,200 nights in space, using of 64 astronauts on 80 Shuttle missions and 21 astronauts who served aboard the International Space Station.

The researchers found that, even though NASA schedules 8.5 hours of sleep per night for crew members in space flight, the average duration of sleep in space amounted to just under six hours on shuttle missions and just over six hours on ISS missions.

As well, only about 12 percent of all the sleep periods on Shuttle missions and 24 percent on ISS missions lasted seven hours or more, compared to 42 percent and 50 percent, respectively, during a post-flight data collection interval when most astronauts slept at home.

The study also showed episodes of sleep deprivation started long before the crew members actually lifted into space, with individual astronauts averaging less than 6.5 hours sleep per night during mission training intervals approximately three months prior to launch.

The research also focused on the apparently pervasive and routine use of sleeping medications such as zolpidem and zaleplon during flight, with 75 percent of the ISS crew members survey indicating they took sleep medication at some point during their time on the space station and about 78 percent of Shuttle-mission also saying they used medication on more than half of the night they were in space.

"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," lead study author Laura K. Barger, an associate physiologist in the BWH Division of Sleep and Circadian Disorders, said in the release. "Routine use of such medications by crew members operating spacecraft are of particular concern, given the U.S. Federal Drug Administration warning that patients using sleeping pills should be cautioned against engaging in hazardous occupations requiring complete mental alertness or motor coordination ... 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."

The ability for crew members to perform at the best of their ability "if awakened from sleep by an emergency alarm may be jeopardized by the use of sleep-promoting pharmaceuticals," said Barger.

The work concludes more effective countermeasures within the program are needed to promote sleep during missions and optimize human performance.