Sleep and Circadian Rhythm During a Short Space Mission

An experiment was conducted to assess sleep and circadian regulation in an astronaut. Sleep was recorded polygraphically on tape as was body temperature. Daytime alertness was subjectively rated by a mood questionnaire. For a comparison, the same parameters were measured during a baseline period preceding the flight. The circa- dian rhythms of body temperature and alertness were found to be de- layed in space compared to baseline. This could mark a phase shift or the transition to a circadian state of free-run. Sleep was shorter and more disturbed. The structure of sleep was significanly altered. In space, REM-latency was shorter, there was less REM sleep in the second non-REM/REM cycle, and slow wave sleep was redistributed from the first to the second cycle