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

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.