Sleep deprivation, which is a potentially dangerous condition in the intense environment of off-world living , is common among astronauts and an important issue for NASA. This is true both for the time astronauts are actually in space, as well as the weeks leading up to liftoff.
A 10-year academic research project partnered with NASA, which was published in yesterday’s edition of The Lancet Neurology, looked at information gathered from 85 astronauts, 75 percent of those whom participated in space shuttle missions and 25 percent were involved in missions aboard the International Space Station (ISS).
While on board, NASA astronauts are scheduled for eight and one-half hours of sleep each “night.” However, the mean duration of sleep was only 5.96 hours on shuttle missions and just slightly more for those onboard the ISS. Those on board the shuttle were recorded as sleeping seven hours only 12 percent of the time, while mission specialists on the ISS slept seven hours 24 percent of the time. On the other hand, the same astronauts sleep seven hours 42 percent and 50 percent of the time (respectively) during post-flight evenings.
Looking at both objective and subjective assessments of sleep quality, the study recorded data of over 4,200 sleep episodes in space and over 4,000 nights of sleep on Earth. Data was collected by an ActiGraph worn on the astronauts’ wrists to record sleeping and waking cycles. The astronauts themselves recorded their own alertness levels and their perception of the quality of sleep the previous evening.
The study, which was partially funded by the National Aeronautics and Space Administration, brought together experts from the Harvard Medical School Division of Sleep Medicine, the University of Colorado Sleep and Chronobiology Laboratory, and Brigham and Women’s Hospital Division of Sleep and Circadian Disorders. In addition to noting the significant decrease in sleep while in space, the study also showed that such deficits begin before the astronauts ever get off the ground. During the pre-flight training period of 12 weeks, study participants averaged 30 minutes less sleep than the average American adult, or less than six and one-half hours per night.
Seventy-five percent of crew members used prescription drugs to help in obtaining and maintaining sleep. Drugs specifically mentioned in the report include Zapelon (branded as Sonata or Andante) and Zolpidem (branded as Stilnox and Ambien). Such medications were used for more than half of the onboard “nights.”
The lead author of the study, Laura K. Barger, pointed out that “performance detriments” are known to occur among those who sleep less than six hours. An associate physiologist in the Brigham and Women’s Hospital, Barger reiterated that deficiencies among space crew members are pervasive and potentially dangerous.
Barger warned that, if awakened because of emergency, prescription sleep drugs could keep affected astronauts from optimal performance. She referred to the U.S. Food and Drug Administration’s warning that the use of sleeping pills should be avoided by people involved “in hazardous occupations requiring complete mental alertness or motor coordination.”
Barger said this is especially important because it is quite possible that “all crew members on a given mission may be under the influence of a sleep promoting medication at the same time.” A senior author of the study, Dr. Charles Czeisler, said that future space missions should include protocols to supplement or replace sleeping pills. These methods could include specifically scheduled exposures to certain wavelengths of light, scheduling modifications, and behavioral strategies. NASA issued a follow-up statement, saying it “is committed to sending humans farther into space than ever before and we need to fully understand the implications of that prior to embarking on a mission.”
By Gregory Baskin