Diurnal cortisol pattern of shift workers on a workday and a day off

摘要

Objectives The aim of this study was to determine how the diurnal rhythm of the hypothalamus-pituitary-adrenal axis is affected by a fast forward-rotating 24-hour shift schedule and to explore possible relationships with self-reported health, sleep-related problems, and recovery-related problems. Methods Shift workers on their morning (N=45) or afternoon (N=32) shift were compared with daytime workers (N=39) from the same worksite and with an external daytime working reference group with early (N=50) or late (N=130) waking. Cortisol in saliva was sampled at waking, after 30 minutes, after 8 hours, and at 2100 on a daytime workday for all of the groups and also on a day off for the shift workers. Sleep and subjective health complaints were assessed with a questionnaire. Results The morning shift workers showed a deviant cortisol pattern over the workday, with a lower cortisol level at waking and a lower morning peak level. The morning and afternoon shift workers did not differ with respect to the cortisol level on the day off. The shift workers also reported lower self-rated health and more problems with sleep and recovery. Conclusions The results suggest that a partial adaptation of the circadian cortisol rhythm to night work does not re-adjust during 4 days off, and hence the early waking on morning shift days occurs during an earlier phase of the diurnal cortisol rhythm than for daytime workers waking up at similar hours. The results may contribute to the understanding of reduced alertness during morning shifts and have implications for the planning of, and adaptation to, shift schedules.