Melatonin, sleep, and shift work adaptation

Badground: Night work is associated with disrupted circadian rhythms, fatigue, accidents, and chronic disease. Melatonin secretion helps regulate sleep ant circadian rhythms. Objective: Melatonin, sleep disturbances, and symptoms (sleep, fatigue, mental) were compared among workers on permanent day, swing and night shy. Methods: Urinary 6-rhydroxymelatonin sulfate (6-OHMS) was measured in postwork and postsleep samples. Disrupted circadian melatonin production was evaluated using the sleep: work 6-OHMS ratio. Wrist actigraphy characterized light exposures and sleep characteristics. Results: Night workers had altered melatonin, disrupted sleep, and elevated symptom prevalence. Subjects grouped by their sleep:work 6-OHMS ratio rather than shift had even greater symptom prevalence. Risks for two or more symptoms were 3.5 to 8 times greater among workers with sleep: work ratios <= 1 compared to those with ratios > 1. Conclusions: This ratio may help identify workers at increased risk for accidents or injuries.