Experimental 12-Hour Shift of the Sleep-Wake Cycle in Man: Effects on Sleep and Physiologic Rhythms.
NIOSH 1981 Jul:125-149
Two long term controlled phase shift experiments using ten healthy men ages 22 to 38 were described. Five subjects lived for 3 weeks in a clinical metabolic research unit. Each subject was confined to bed in a totally darkened and sound isolated room from 10 p.m. until 6 a.m. for 7 nights. On day eight, subjects were kept awake until 10 a.m. and thereafter were allowed to sleep from 10 a.m. until 6 p.m. The second protocol involved five different subjects in another metabolic research unit for a total of 9 weeks. Sleep was set from 11 p.m. until 7 a.m. for 21 days and reversed on day 22. Thereafter, sleep was from 11 a.m. to 7 p.m. until day 43 when it was returned to the original schedule. Polygraphic sleep parameters, body temperature, and blood levels of growth hormone and cortisol were monitored. The 12 hour inversion of sleep wake period under controlled conditions produced shortened sleep latency, shortened rapid eye movement (REM) stage latency, and increased amount of REM sleep during the first 2 hours of sleep. Early awakenings occurred during hours five to eight, and all sleep stages were reduced during final hours of sleep periods. Increased numbers of sleep stage changes persisted for approximately 2 weeks after acute sleep reversal. Nonsleep parameters were delayed in reference to polygraphic parameters such that no complete phase inversions were noted. All parameters rapidly returned to baseline levels after backreversal at day 43 of the 9 week protocol, suggesting that subjects had not fully adapted to the reversed situation. The authors suggest that social synchronizers, lighting, or other factors producing subtle perturbations of circadian rhythm, contribute to lack of complete phase inversion for nonsleep parameters and that similar perturbations could affect night workers, leading to disturbances similar to those experienced by the experimental subjects regardless of any change in sleep patterns.
NIOSH-Grant; Worker-health; Work-intervals; Humans; Sleep-deprivation; Endocrine-function; Physiological-response; Psychological-effects; Biological-rhythms;
The Twenty-Four Hour Workday: Proceedings of a Symposium on Variations in Work-Sleep Schedules, Division of Biomedical and Behavioral Science, NIOSH, U.S. Department of Health and Human Services, Cincinnati, Ohio, DHHS (NIOSH) Publication No. 81-127