Land of nod still some way off (Image: NASA)

It’s easy to drift in space, but it’s harder to drift off to sleep. The most comprehensive study to date of sleep patterns in astronauts reveals that they suffer sleep deficiency during space flight and even before they take off – and sleeping pills may not be the solution.

Astronauts have complained of fatigue and sleep deficiency since the beginning of human space travel.

“Trying to sleep in space is a neat kind of disorientation,” says six-time NASA astronaut Story Musgrave. “There’s no clock, no day or night, no up or down, and no tension on your body so you can even lose the sense of where your limbs are when you sleep.”


Most astronauts can expect a relatively quick return to normal, as most space missions last a year or less. But as space agencies prepare for longer journeys to Mars or elsewhere in the solar system, it will become ever more important to understand how best to manage sleep in space.

Now, researchers from Brigham and Women’s Hospital and Harvard Medical School in Boston have performed the most extensive analysis to date. They monitored the sleep patterns of 64 astronauts from 80 space shuttle missions, as well as 21 astronauts who spent time on the International Space Station. They fitted the astronauts with a wrist device that records sleep and waking cycles and required them to keep a diary of their sleep habits before, during and after space flight, logging more than 4200 nights in space and over 4000 on Earth in total.

Despite having 8-and-a-half hours in every 24 designated for sleep during space flight, the average astronaut slept just under 6 hours on shuttle missions, and just over 6 hours on ISS visits. Only 12 per cent of shuttle astronauts and 24 per cent of those on the ISS slept more than 7 hours at a time.

The researchers found that preflight sleepless nights are also common, and sleep deficiency can build up in astronauts from as early as three months before lift-off. Astronauts in training average only 6.5 hours per night – although that is not far off from average adults during the work week, says researcher Laura Barger of Harvard Medical School.

Things improved once the astronauts were back on the ground, though. Post-flight data recorded for the same astronauts showed that they slept more than 7 hours nearly half the time once they returned to Earth.

Lack of sleep has been consistently linked to decreased performance, and more effective measures are needed to keep crew members as alert as possible. While some astronauts cope with disorientation by sleeping in a closet in a sort of sleeping bag, or strapping down their knees or head, Barger and her colleagues found that more than 75 per cent of astronauts turn to sleep medication at some point.

“Medication is essential. After two to three days of bad sleep, your performance begins to suffer, and often medication is the only relief,” says Musgrave.

While this strategy is common, it might not the best remedy. “If astronauts had to be awakened in an emergency situation, they run the risk of their performance being impaired if they’ve been using hypnotic sleep aids,” says Barger.

The ISS is testing out new lighting that provides more short-wavelength light to promote alertness. Future research will explore behavioural changes and schedule modifications that might help astronauts to sleep through the “night”.

Journal reference: The Lancet Neurology, doi.org/t37