Astronaut Jeffrey A. Hoffman barely slept in the days leading up to his first space shuttle mission in 1985. And the adrenaline rush during the flight kept him up, so he spent his nights staring out the window instead of sleeping the eight hours NASA allotted.
On the third day of the mission, he was falling asleep while performing a task, and crew members shouted at him to wake up. So he began taking sleeping pills to improve his performance.
His experience was not at all unusual, according to a study published Thursday by Boston and Colorado researchers. Three-quarters of astronauts in the 10-year study reported using sleeping pills such as zolpidem and zaleplon during nights in space, a worrisome finding because the medications can jeopardize the ability to quickly wake up and respond to emergencies, the researchers said in the study published in the journal The Lancet Neurology.
Sleeping pills come with warnings that the ability to drive or operate heavy machinery could be impaired.
Most astronauts do not sleep enough in the months leading up to a mission and during the mission, even though NASA allots 8.5 hours of sleep per night for crew members, the researchers from Brigham and Women’s Hospital, Harvard Medical School, and the University of Colorado found.
“The concern is if there’s an emergency situation and crew members have just taken hypnotics, they might not perform as well. You have to weigh the benefits of hypnotics against those risks,” said Dr. Laura K. Barger, the lead author and an associate physiologist in the Brigham’s Division of Sleep and Circadian Disorders. “We need to have better countermeasures to improve sleep.”
NASA, which funded the study, issued a statement, saying, “Our astronauts work in harsh, complex environments where they are sometimes subjected to uncomfortable and high stress situations. The agency works hard to identify and implement countermeasures that can ensure astronauts are able to get the same quality and quantity of sleep in space as they do on Earth. ... The agency 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 to Mars.”
Researchers recorded more than 4,000 nights of sleep on Earth and more than 4,200 nights in space from 2001 to 2011, the largest-ever study of sleep during space flight. Astronauts often complain of fatigue and sleep deprivation, the researchers wrote, and the findings suggest that sleep problems begin up to three months before space missions, during training.
“If people are having problems sleeping, that’s a risk to mission success,” said Hoffman, now a professor at the Massachusetts Institute of Technology. “If something goes wrong, you want people to be at their peak in order to deal with it.”
The study looked at astronauts on shuttle missions, which typically last one to two weeks, and long-duration missions, which are up to six months. Although researchers expected astronauts on long-duration missions would sleep better, they only averaged a few minutes more sleep than shuttle mission astronauts -- each group averaged about six hours a night. During training, they got a bit more shuteye, but still less than 6.5 hours.
Researchers do not know whether medications are metabolized differently in space than on Earth, and whether different doses should be given as a result, said Dr. Dorit Donoviel, deputy chief scientist at the National Space Biomedical Research Institute, a partner of NASA that helped pay for the study. Further studies are planned to examine whether sleep requirements differ in space, she added, noting that individual astronauts also have varying sleep patterns.
“To keep humans healthy” in space, she added, “we have to understand how much sleep (they need) and how to allow them to get the sleep they need to perform at their peak.”
For a planned manned mission to Mars, which would run for at least a year, improving sleep patterns is more important than ever, said Barger, of the Brigham.
When orbiting Earth, light and dark alternate every 90 minutes, disrupting circadian sleep patterns, Hoffman said. In 1990, his crew was scheduled to launch at midnight, but the astronauts were worried they would not be fully alert.
A Harvard researcher proposed shifting their circadian rhythms so they would be prepared for the mission. The crew members were put in an all-white room where bright fluorescent lights shone at midnight, and darkness fell in the middle of the day. Their bodies adjusted in about two days. Now, all astronauts go through the process before each mission.
“If you’re sleep-deprived, you start to make cognitive mistakes,” Hoffman said. “Long-duration space flight has a whole new set of challenges with respect to sleep.”