Rotating Nightshift Work and Hematopoietic Cancer Risk in US Female Nurses

Abstract

Abstract Background Nightshift work is a plausible risk factor for hematologic cancer, but epidemiological evidence remains sparse, especially for individual subtypes. We prospectively examined the association of rotating nightshift work with hematopoietic cancer risk. Methods This cohort study included US women from the Nurses’ Health Study (NHS: n = 76 846, 1988–2012) and Nurses’ Health Study II (NHSII: n = 113 087, 1989–2013). Rotating nightshift work duration was assessed at baseline (both cohorts) and cumulatively updated (NHSII). Cox regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for overall hematopoietic cancer and specific histologic subtypes. All statistical tests were two-sided. Results We documented 1405 (NHS) and 505 (NHSII) incident hematopoietic cancer cases during follow-up. In NHS, compared with women who never worked rotating nightshifts, longer rotating nightshift work duration was associated with an increased risk of overall hematopoietic cancer (HR1–14y = 0.93, 95% CI = 0.83 to 1.04; HR≥15y = 1.28, 95% CI = 1.06 to 1.55; Ptrend = .009). In NHSII, results were similar though not statistically significant (HR1–14y = 0.99, 95% CI = 0.82 to 1.21; HR≥15y = 1.41, 95% CI = 0.88 to 2.26; Ptrend = .47). In the subtype analyses in the NHS, the association of history of rotating nightshift work with risk of diffuse large B-cell lymphoma varied by duration (HR1–14y = 0.71, 95% CI = 0.51 to 0.98; HR≥15y = 1.69, 95% CI = 1.07 to 2.67; Ptrend = .01) compared with those who never worked rotating nightshifts. Women reporting a longer history of rotating nightshifts also had suggestive (statistically nonsignificant) increased risks of overall non-Hodgkin lymphoma (HR≥15y = 1.19, 95% CI = 0.95 to 1.49), Hodgkin lymphoma (HR≥15y = 1.32, 95% CI = 0.43 to 4.06), and multiple myeloma (HR≥15y = 1.42, 95% CI = 0.85 to 2.39). Conclusions Longer duration (≥15 years) of rotating nightshift work was associated with increased risks of overall and several subtypes of hematopoietic cancer.