Laura K. Barger, associate physiologist in the BWH Division of Sleep and Circadian Disorders, said that sleep deficiency was pervasive among crew members and 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.
The results also suggested 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 highlighted 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 percent) of shuttle-mission crew members used medication on more than half (52 percent) of nights in space.
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 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.
The study concluded that more effective countermeasures to promote sleep during space flight are needed in order to optimize human performance.
The study is published in The Lancet Neurology.