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.
From the Department of Community Health and Epidemiology (Mr McPherson, Dr Janssen, Ms Grundy, and Drs Tranmer, Richardson, and Aronson), Cancer Research Institute (Mr McPherson, Ms Grundy, and Drs Richardson and Aronson), School of Kinesiology and Health Studies (Dr Janssen), and School of Nursing (Dr Tranmer), Queen's University, Kingston, Ontario, Canada.
Address correspondence to: Kristan J. Aronson, PhD, Department of Community Health and Epidemiology, Queen's University, Division of Cancer Care and Epidemiology, 10 Stuart St, Kingston, ON K7L 3N6, Canada (email@example.com).
Authors Mark McPherson, Ian Janssen, Anne Grundy, Joan Tranmer, and Harriet Richardson received funding from the Workplace Safety and Insurance Board of Ontario. Student funding was also provided by the Heart and Stroke Foundation of Ontario.
The JOEM Editorial Board and planners have no financial interest related to this research.