Circadian Rhythms: Interference with and Dependence on Work-Rest Schedules.
NIOSH 1981 Jul:13-50
Circadian rhythms were assessed with regard to research on plasticity and rigidity, and applications to work rest schedules were discussed. Patterns of circadian rhythms were noted for personal tempo, acoustic adaptation, rectal temperature, oral temperature, pulse rate, axillary temperature, skin resistance, plasma cortisol and renin levels, urine volume, and normal daytime activity under conditions of normal and altered sleep wake cycles. Data were summarized from several studies. Results illustrated the ability of the circadian system to remain rhythmic under extremely adverse conditions and also demonstrated that environmental entrainment could be lost despite presence of a behavioral time structure. The author emphasized that sleep wake cycle contributed to phase control of other rhythms, citing studies of interdependencies between sleep wake cycle and hormone levels and between sleep wake cycle and body temperature. Key points of studies of circadian cycle kinetics were summarized with application to flight across time zones and shift work. The circadian system did not regain stable phase relationships until after several transient periods. Rate of shift per day varied during reentrainment, due in part to phase response curve shape. The mean rate at which reentrainment occurred differed between variables and depended upon the direction of shift. The author noted that simulated shift work created a situation in which it was difficult to derive true behavior of the circadian system from patterns of overt rhythms and suggested that similar circumstances occur after prolonged night work. Many patterns seen during shift work could be attributed to selective entrainment and masking. The author concludes that various obstacles opposing perfect adjustment of the circadian system to night work indicate that shifts minimized and that analysis of the bidirectional interaction between sleep wake cycle and other circadian system components represents a major task for research in work rest schedules.
Worker-health; Work-performance; Biological-rhythms; Work-intervals; Job-stress; Sleep-deprivation; Endocrine-function; Physiological-response; Psychological-effects; Worker-motivation;
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