Rotating nightshift work and the risk of endometriosis in premenopausal women
Eva S Schernhammer1, Allison F Vitonis, Janet Rich-Edwards
1Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA. eva.schernhammer@channing.harvard.edu
Objective:
The purpose of this prospective study was to study the association between rotating nightshift work and endometriosis risk within the Nurses' Health Study II.
Study Design:
We found 89,400 women without diagnosed endometriosis at baseline; the 2062 laparoscopically confirmed cases that were documented during 16 years of follow-up evaluation formed our study population.
Results:
Overall, there was no association between rotating nightshift work and risk of endometriosis. When the cases were categorized by infertility status, risk was elevated among women with concurrent infertility and ≥5 years of rotating nightshift work (rate ratio, 1.71; 95% confidence interval, 1.18-2.49; P(trend) = .005), compared with women with no rotating nightshift work. In contrast, there was no association among women without reported infertility (P(heterogeneity) = .003).
Conclusion:
Women who work rotating nightshifts for ≥5 years may have a modestly elevated risk of endometriosis if concurrently infertile. However, the relation between shiftwork, endometriosis, and infertility is complex, and the potential for bias because of a healthy or infertile worker effect must be considered.
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