Shorter sleep duration, more wakefulness, and changes in the sleep cycle brought on by microgravity make it tough for astronauts to get a good night’s sleep while they’re in outer space, a new study shows.
In research that has implications for earthlings as well as astronauts, scientists found that the “significant sleep changes induced by the extreme environmental conditions of spaceflight can magnify and help reveal similar, though potentially less noticeable, changes that are induced by the more moderate conditions of Earth.
“Our results support other studies indicating that sleep architecture can adapt to different environments. Also, the sleep deficits that our subjects were facing while working around the clock in a high-pressure environment provide further evidence for the danger of stress and shift-work schedules for humans anywhere,” study investigator Oliver Piltch, an undergraduate researcher at Harvard University, Cambridge, Massachusetts, said in a release.
The findings were presented at Virtual SLEEP 2020, the 34th annual meeting of the Associated Professional Sleep Societies.
High Rate of Hypnotic Use
The researchers studied sleep architecture in four cosmonauts and one astronaut before, during, and after missions to the Mir space station.
Using the NightCap sleep monitor, they recorded a total of 324 nights of sleep ― 112 pre-flight nights, 83 in-flight nights, and 61 post-flight nights.
Despite having the same “sleep opportunity” in space as on earth, the astronauts were on average sleeping an hour less each night during the space mission compared to when on earth before or after their mission (5.7 vs 6.7 hours; P < .0001).
In space, the astronauts also spent significantly more time awake in bed, leading to a 17.7% reduction in sleep efficiency.
Sleep architecture was also affected by spaceflight. In space, the time in non–rapid eye movement (non–REM) and REM sleep decreased by 14.1% and 25.8%, respectively. On average, it took about 90 minutes after falling asleep for astronauts to reach their first episode of REM sleep in space ― nearly 1.5 times longer than on earth.
“There were marked shifts in sleep architecture compared to baseline, and some of these evolved over the course of the mission,” said Piltch.
“Our findings were consistent with previous studies that focus on the issue of sleep continuity. We found significant decreases in sleep efficiency during spaceflight despite similar times in bed,” he noted.
Piltch said it’s important to understand how sleep is affected by spaceflight in order to better equip astronauts for success on long-duration flights, such as a trip to Mars or the Moon.
He also pointed to a recent study in The Lancet Neurology that showed that 78% of the international space station crew take hypnotics on 52% of nights in space. “So it doesn’t look like they sleep very well in space,” he said.
Reached for comment, Camilo A. Ruiz, DO, medical director, Choice Physicians Sleep Center, Fort Lauderdale, Florida, said the findings add to the “limited” data currently available on sleep in space and microgravity.
“To a certain point, the results of this study could have been expected, since sleep continuity and sleep architecture disruption is present during stressful periods of human life or in changes to the sleep rituals we hold dear, such as our beds and quiet bedrooms,” said Ruiz, who was not involved in the study.
“The potential harm to astronauts from their sleep continuity and deranged sleep architecture is that the decreased alertness, performance, vigilance, and psychomotor skills they exhibit in that high-stakes environment such as space flight can lead to serious accidents that can jeopardize the safety of the crew and vessel,” Ruiz noted.
“These research areas are on the forefront of space medicine that will allow mankind to lead successful interplanetary missions and colonization of these planets with long-term resident astronauts,” he added.
The study was supported by funding from the Mary Gordon Roberts Fellowship, the National Academy of Sciences, the National Institute of Mental Health, the MacArthur Foundation Mind-Body Network, and Healthdyne Technologies. Piltch and Ruiz have no disclosed no relevant financial relationships.
SLEEP 2020: 34th Annual Meeting of the Associated Professional Sleep Societies: Abstract 0278, presented August 28, 2020.
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