Night shift work and risk of melanoma: a prospective cohort study among 59,384 female nurses in the Netherlands.

Abstract

Background: Night shift work may be a risk factor for melanoma, potentially due to suppressed melatonin and decreased vitamin D levels. We examine the potential association between night shift work and melanoma risk using detailed, lifetime information on night shift work in a large cohort of Dutch nurses.

Methods: We used questionnaire data from the Nightingale Study obtained from 59,384 (former) female nurses aged 19-65 (median: 48.7 years; interquartile range: 39.6-55.3). Hazard ratios (HR) and 95% confidence intervals (95%CI) for melanoma risk in relation to various lifetime night shift work exposure variables were estimated.

Results: During 10 years of follow-up, 307 women developed melanoma. Melanoma risk did not differ between women who worked night shifts and those who never worked night shifts (age-adjusted HR=0.98; 95%CI=0.73-1.30). No statistically significantly increased risks were found for a longer night shift work duration, a higher cumulative number of nights worked, a higher number of consecutive nights worked per month, or a shorter time since quitting night shift work.

Conclusion: We found no association between night shift work exposure and melanoma risk.

Impact: This study should reassure nurses that working night shifts is not associated with an increased risk of melanoma.