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Melatonin, Sleep, and Shift Work Adaptation

Burch, James B. PhD; Yost, Michael G. PhD; Johnson, Wendy MS; Allen, Emily MS

Journal of Occupational and Environmental Medicine: September 2005 - Volume 47 - Issue 9 - p 893-901
doi: 10.1097/01.jom.0000177336.21147.9f
Original Articles

Background: Night work is associated with disrupted circadian rhythms, fatigue, accidents, and chronic disease. Melatonin secretion helps regulate sleep and circadian rhythms.

Objective: Melatonin, sleep disturbances, and symptoms (sleep, fatigue, mental) were compared among workers on permanent day, swing, and night shifts.

Methods: Urinary 6-hydroxymelatonin 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.

From the Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, Colorado (Dr Burch, Ms Johnson); and the Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington (Dr Yost, Ms Allen).

Supported by research grant number 5 R01 OH03885-02 from the National Institute for Occupational Safety and Health, National Institutes of Health.

James Burch has no financial interest related to this article.

Address correspondence to: James Burch, MS, PhD, Assistant Professor, Department of Epidemiology and Biostatistics, University of South Carolina, 2221 Devine St, Room 237A, Columbia, SC 29036. E-mail:

©2005The American College of Occupational and Environmental Medicine