Effect of night-shift work on cortisol circadian rhythm and melatonin levels

OBJECTIVES: Night-shift work has been associated with several negative effects on worker’s health, possibly due to circadian desynchronization, sleep deprivation and suppression of nocturnal melatonin secretion including exposure to light during the work shift. The objective of this study was to evaluate the impact of fixed night-shift work versus day-shift work on the sleep-wake cycle and on the night and day levels of cortisol and melatonin. MATERIAL AND METHODS: Saliva samples were obtained from 36 individuals, 19 day workers (12 women and 7 men) and 17 night workers (12 women and 5 men) from a university hospital in southern Brazil, with no history of chronic diseases. Demographic and personal information were obtained through a self-administered questionnaire and sleep information by the Munich chronotype questionnaire. RESULTS: Salivary cortisol showed normal circadian rhythm in day- and night-shift workers, but was attenuated in night-shift workers during their working hours and on leave days. Night workers sleep fewer hours at night and have higher negative social jet lag than day workers. CONCLUSION: Intervals between night shifts can be beneficial for the recovery of the hypothalamic-pituitary-adrenal axis, minimizing the negative effects on workers’ health, in addition to a preventive approach to aspects related to sleep hygiene and healthy life habits.