Astronauts in orbit suffer from severe, widespread sleep deprivation that could be putting their lives in danger, according to a study published in the medical journal The Lancet Neurology.
Researchers found that astronauts average less than six hours of sleep a night on space shuttle missions and just over six hours on the International Space Station. The sleep deficits occurred despite the American space agency NASA scheduling eight and a half hours of sleep per night for crew members.
The study was led by Dr Laura Barger from Harvard Medical School in Boston. Investigators tracked the sleep patterns of 64 astronauts across 80 space shuttle missions and 21 International Space Station crew members before, during, and after spaceflight.
Heavy reliance on sleeping pills
Around three-quarters of astronauts reported using sleeping pills while in space, raising significant concerns among medical researchers regarding cognitive and physical performance.
"Sleep deficiency is pervasive among crew members," Dr Barger said. "It’s clear that more effective measures are needed to promote adequate sleep in crew members, both during training and spaceflight, as sleep deficiency has been associated with performance decrements in numerous laboratory and field-based studies."
Dr Barger warned that sleeping pharmaceuticals could impair response times during unexpected spaceflight emergencies. "The ability for a crew member to optimally perform if awakened from sleep by an emergency alarm may be jeopardised by the use of sleep-promoting pharmaceuticals," she said. "Routine use of such medications by crew members operating spacecraft is of particular concern."
Government health guidelines advise patients taking sleeping medication to avoid hazardous occupations requiring high mental alertness and physical coordination. Dr Barger noted that this risk is amplified in space because multiple crew members often take medications simultaneously.
"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," Dr Barger explained. On four space shuttle missions where all crew members participated in the study, every astronaut on board reported taking sleeping pills on the same night six percent of the time.
Disrupted light cycles and microgravity
Orbital mechanics contribute heavily to disturbed sleep patterns. Astronauts aboard the International Space Station orbit Earth every 90 minutes, experiencing 16 sunrises and sunsets every 24 hours.
Historically, Apollo astronauts complained that their sleep was interrupted by bright light, background noise, and suit cooling systems. Although modern spacecraft feature dark and quiet sleep stations, sleep disturbances persist, leading researchers to suspect that microgravity itself may disrupt sleep physiology.
The International Space Station is a microgravity laboratory orbiting approximately 250 miles above Earth. NASA, the National Aeronautics and Space Administration, oversees American crew operations aboard the station.
Sleep loss begins long before launch
The study revealed that sleep deprivation begins months before astronauts ever leave Earth. During training approximately three months prior to launch, crew members averaged less than six and a half hours of sleep per night, which is about 30 minutes less than the average American adult.
To record sleep cycles, researchers fitted astronauts with an actigraph, a specialized wrist-worn monitor that tracks sleep and wake periods. Scientists also evaluated daily diary entries written by crew members detailing their alertness levels and sleep quality.
Sleep duration improved significantly after crew members returned to Earth, with at least half of the astronauts gaining much more rest. Only 12 percent of sleep sessions on space shuttles and 24 percent on the space station lasted seven hours or more, compared with 42 percent and 50 percent respectively after missions ended.
Preparing for deep space exploration
Study co-author Dr Charles Czeisler, also from Harvard Medical School, emphasized that future deep space missions will require improved sleep management techniques.
"Future exploration spaceflight missions to the moon, Mars, or beyond will require more effective countermeasures to optimise human performance by promoting sleep during spaceflight," Dr Czeisler said. "These may include modifications to schedules, strategically timed exposure to specific wavelengths of light, and behavioural strategies to ensure adequate sleep, which is essential for maintaining health, performance and safety."
Writing in a commentary in The Lancet Neurology, Dr Mathias Basner from the University of Pennsylvania called for expanded research into spaceflight sleep mechanics, noting that only four people have consecutively lived and worked in space for more than one year.
"As such, how sleep and behavioural health will be affected during space exploration is poorly understood," Dr Basner wrote. "Studies of the physiology of sleep stages and the intensity of sleep.. in space are necessary to answer the important question of whether spaceflight reduces the need for sleep and therefore the ability to sleep, or whether it reduces the ability to sleep but not the need for sleep."
Developing synthetic leaves for spaceflight
In addition to sleep management, researchers are examining new life support solutions for long space journeys. Designer and art graduate Julian Melchiorri has developed a functioning man-made leaf that produces oxygen by absorbing water and carbon dioxide.
The synthetic leaf material is constructed by suspending chloroplasts from plant cells within a matrix of silk protein extracted from natural silk fibres. Melchiorri claimed the material could supply continuous oxygen for long space missions or planetary colonization, where natural plants cannot grow due to zero gravity.
Microgravity toilet design and operation
Living in orbit also requires specialized equipment for daily hygiene. Montana-based scientist Hank Green detailed the mechanics of zero-gravity toilets in a recent video explanation.
"The toilet itself works like a vacuum cleaner, using differential air pressure to suck the solid waste away," Green explained. Astronauts use body restraints to remain secured to the seat during use.
Standard toilet seats on Earth measure between 12 and 28 inches (30 to 45 centimetres) in diameter, but space toilet openings for solid waste are only about four inches (ten centimetres) wide. To ensure proper positioning, NASA trains astronauts using a specialized practice toilet fitted with an internal camera.
Solid waste is stored on the space station and later loaded onto returning capsules for disposal on Earth, while liquid waste is processed and recycled into life-essential systems on the ISS.
