Sleeping In Space

Sleep researchers are learning new and surprising things about sleeping in space.

Space travel is sleepless work.

Despite NASA recommendations that astronauts sleep 8 hours a day, they usually don't. Strange sights and sounds, the stress of riding a powerful rocket, the lack of a normal day-night cycle - all these things tend to keep space travellers awake. Studies show that astronauts typically sleep 0.5 to 2.5 hours less than they do on Earth.

Although many astronauts report feeling fully rested after only six hours of sleep, the fact is, sleeplessness can cause irritability, forgetfulness and fatigue - none of which astronauts need to deal with while piloting complicated 'ships that hurtle through space at tens of thousands of miles per hour.

The solution seems simple: Take a nap.

Could you sleep like this?

But naps are a double-edged sword. Sometimes napping can leave you feeling even drowsier than before. If your body enters a deep sleep, trying to wake after only an hour or so can be very unpleasant, and you might remain groggy for some time afterward. This is called "sleep inertia."

Why do naps sometimes backfire? Researchers don't yet know the physical causes of sleep inertia, but they would like to be able to predict, at least, when it's going to strike. This could help doctors prescribe naps of the right time and duration for drowsy people in high-risk professions.

Helping astronauts nap was the goal of a recent series of experiments funded by NASA in cooperation with the National Space Biomedical Research Institute. In those experiments, led by David Dinges, a professor at the University of Pennsylvania School of Medicine, 91 volunteers spent 10 days living on one of 18 different sleep schedules, all in a laboratory setting. The sleep schedules combined various amounts of "anchor sleep," ranging from about 4 to 8 hours in length, with daily naps of 0 to 2.5 hours.

To measure how effective the naps were, the scientists gave the volunteers a battery of tests probing memory, alertness, response time, and other cognitive skills throughout the experiment. They also measured things like core body temperature and hormone levels in blood and saliva, all of which fluctuate in a natural daily cycle known as a person's "biological clock."