Sleep and Circadian Rhythms in Four Orbiting Astronauts

This experiment measured the sleep and circadian rhythms of four male astronauts aboard a space shuttle (STS-78) orbiting the Earth for 17 days. The space mission was specially scheduled to minimize disruptions in circadian rhythms and sleep so that the effects of space flight and microgravity per se could be studied. Data were collected in 72-h measurement blocks: one block 7 days before launch, one early within the mission (3 days after launch), one late in the mission (12 days after launch), and one 18 days after landing. Within each measurement block, all sleep was recorded both polysomnographically and by sleep diary. Core body temperature was sampled every 6 mins. Actillumes© were worn continuously. All urine samples were collected separately. Performance was assessed by a computerized test battery (3/day) and by end-of-shift questionnaires (1/day); mood and alertness were measured by visual analogue scales (5/day). Circadian rhythms in orbit appeared to be very similar in phase and amplitude to tho...