Researchers Say Sleep in Space Less than Restful SpaceDaily

After three months in space, astronauts lose sleep and sleep less soundly because the lack of gravity and the absence of day-and-night cues throw off their internal clocks, according to the first long-term study of the topic. Space sleeplessness is apparently caused by changes in the brain’s endogenous circadian pacemaker _ a bundle of nerve cells the size of a pinhead that controls the body’s cycle of sleep and wakefulness.