NASA expects astronauts to get around 8.5 hours of sleep per night, but a new study revealed each crew members in spaceflight get a little over 2.5 hours less sleep every day.

The study, released this week, said that astronauts suffer a great deal of sleep deficiency in the weeks leading up to and during spaceflight.

Duration of sleep during spaceflight was just under six (5.96) hours on shuttle missions and six hours (6.09) on ISS missions.

Approximately 12 percent of sleep episodes on shuttle missions and 24% on ISS missions lasted seven hours or more, compared with 42% and 50% in a post-flight data collection interval when most astronauts slept at home, according to the study.

"Sleep deficiency is pervasive among crew members," said Dr. Laura K Barger from Brigham and Women's Hospital, according to The Times of India. "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".

Results suggest that astronauts' build-up sleep deficiency starts before launch, as they averaged 6.5 hours of sleep per night during training.

This is about half an hour less per night than the average American adult.

Sleep deficiency and fatigue are common complaints among astronauts, but this is the most detail study to include both objective evaluation of sleep and subjective evaluations.

"The ability for a crew member to optimally perform if awakened from sleep by an emergency alarm may be jeopardized by the use of sleep-promoting pharmaceuticals," said Dr. Barger. "Routine use of such medications by crew members operating spacecraft are of particular concern, given the FDA warning that patients using sleeping pills should be cautioned against engaging in hazardous occupations requiring complete mental alertness or motor coordination, including potential impairment of the performance of such activities that may occur the day following ingestion of sedative/hypnotics."

For the study, researchers from Brigham and Women's Hospital, Harvard Medical School and the University of Colorado studied sleep patterns of 64 astronauts on 80 shuttle missions and 21 astronauts aboard International Space Station (ISS) missions before, during, and after spaceflight.

They recorded more than 4,000 nights of sleep on Earth, and 4,200 in space in total.

"Future exploration spaceflight missions to the Moon, Mars, or beyond will require more effective countermeasures to optimize human performance by promoting sleep during spaceflight," said Co-author Dr. Charles Czeisler, according to The Times of India. "These may include modifications to schedules, strategically timed exposure to specific wavelengths of light and behavioral strategies to ensure adequate sleep, which is essential for maintaining health, performance and safety."

The spaceflight environment, where the sun rises and sets every 90 minutes, makes it hard for astronauts to get a normal night's sleep.

Apollo astronauts said noise, light, and the cooling systems in spacesuits all prevented them from getting 8 hours of sleep. 

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