McPherson, M., Janssen, I., Grundy, A., Tranmer, J., Richardson, H., Aronson, K.J. Physical activity, sedentary behavior, and melatonin among rotating shift nurses. Journal of Occupational and Environmental Medicine, 2011; 53(7):716-721.
OBJECTIVE: To determine the effect of physical activity and sedentary behavior on melatonin levels in a group of rotating shift nurses.
METHODS: Physical activity and sedentary behaviors for 118 nurses were recorded during both a day shift and a night shift using activity diaries, and concentrations of urinary 6-sulfatoxymelatonin were analyzed for each shift.
RESULTS: During the day shift, energy expended in moderate- and vigorous-intensity physical activity between 3 PM and 7 AM was negatively associated with melatonin levels (P = 0.024). During the night shift, energy expended in sedentary behaviors was negatively associated with melatonin levels (P = 0.008).
CONCLUSIONS: Physical activity and energy expended in sedentary behavior are inversely associated with morning urinary melatonin concentrations. Nevertheless, energy expenditure explains a relatively small amount of melatonin variation, perhaps suggesting that peak melatonin is minimally affected by these patterns of physical activity.