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Journal of Occupational & Environmental Medicine:
doi: 10.1097/JOM.0b013e31822282fd
ORIGINAL ARTICLES: CME Available for this Article at

Physical Activity, Sedentary Behavior, and Melatonin Among Rotating Shift Nurses

McPherson, Mark MSc; Janssen, Ian PhD; Grundy, Anne MSc; Tranmer, Joan PhD; Richardson, Harriet PhD; Aronson, Kristan J. PhD

Continued Medical Education
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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.

©2011The American College of Occupational and Environmental Medicine


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