Shift work and the jet-lag syndrome: conflicts between environmental and body time.
Fuller CA; Sulzman FM; Moore-Ede MC
The twenty-four hour workday: proceedings of a symposium on variations in work-sleep schedules. Johnson LC, Texas DI, Colquhoun WP, Colligan MJ, eds. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 81-127, 1981 Jul; :305-320
The body's response to fatigue and sleep loss, and conflict between external time and rhythmic functions of physiological systems were studied. Observations of two aircraft captains showed that work, sleep, and eating schedules varied randomly when compared with individual's home time. Effects of a single phase shift of light dark (LD) cycle were observed using squirrel-monkeys (Saimiri- sciureus) (SM) as experimental primates. Feeding and drinking rhythms were essentially resynchronized to new LD cycle within 48 hours when LD phase shift was displaced for 8 hours. Temperature rhythm took approximately 24 hours longer to resynchronize. Urinary potassium, sodium, and volume rhythms took approximately 7 days to completely resynchronize. In addition to LD cycles, rhythmic availability of food was a key element affecting an organism's timing. When SMs were concurrently entrained to a LD 12:12 (light and dark for 12 hours each) and an eating fasting (EF) cycle of 3:21 hours (food available for 3 hours and not available for 21 hours), the timing of temperature rhythm was not affected, while all other rhythms were phase shifted by EF cycle. A complex rhythmic behavior was observed when a SM was exposed to an 18 hour day with LD 9:9 cycle. Besides active synchronization of biological rhythms, external time cues could have passive influences on rhythms. Animals synchronized to environmental time cues were able to maintain body temperature without difficulty during cold exposure. Effective thermoregulation required proper temporal synchronization of various physiological systems responsible for maintenance of body temperature. The authors recommend that the fatigue factor should be minimized. Daytime flight should be chosen whenever practical. The temporal environment should be synchronized to present a single unified 24 hour environment. If a shift is required for a short period, the individual should maintain himself on his own time.
Shift-work; Pilots; Sleep-disorders; Environmental-factors; Physiological-disorders; Laboratory-animals; Psychological-fatigue; Psychophysiology; Circadian-rhythms
Johnson LC; Texas DI; Colquhoun WP; Colligan MJ
DHHS (NIOSH) Publication No. 81-127
The twenty-four hour workday: proceedings of a symposium on variations in work-sleep schedules