title: Pre-adaptation to shiftwork in space.
abstract: Astronauts are often required to work in shift schedules. To test pre-mission adaptation strategies and effects on the circadian system, a study was performed using microgravity simulation by head-down bedrest. Eight male subjects were studied over 4 control days, and 7 days each for pre-mission adaptation, bedrest, and readjustment. The circadian system was assessed by monitoring ECG and temperature, and by collecting urine for determination of hormones and electrolytes. Rhythms did not achieve complete adjustment within the adaptation period when the sleep-wake cycle was shortened by 1 h/day, but resynchronization continued during bedrest. After the bedrest period when the time shift was reversed by a 7-h delay within 2 days, resynchronization was achieved satisfactorily only within 7 days. From the results it is concluded that a sleep-wake cycle advance as used in this study is insufficient to keep the circadian system in pace. Under operational conditions the circadian system of astronauts may become longer and more destabilized than under controlled laboratory conditions.
authors.affiliation: DLR-Institute for Aerospace Medicine, Koln, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Samel
authors.forename: H M
authors.initials: HM
authors.lastname: Wegmann
authors.forename: M
authors.initials: M
authors.lastname: Vejvoda
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000337:Aerospace Medicine; D018480:Astronauts; D001510:Bed Rest; D001831:Body Temperature; D002118:Calcium / Q000652:urine; D002940:Circadian Rhythm / Q000502:physiology*; D004562:Electrocardiography; D018475:Head-Down Tilt; D006339:Heart Rate; D006801:Humans; D008297:Male; D008550:Melatonin / Q000031:analogs & derivatives / Q000652:urine; D010561:Personnel Staffing and Scheduling; D011188:Potassium / Q000652:urine; D012964:Sodium / Q000652:urine; D018474:Weightlessness Simulation; D014940:Work Schedule Tolerance
chemical_list: D012964:Sodium; D008550:Melatonin; D011188:Potassium; D002118:Calcium; C012365:6-hydroxymelatonin