Rotating night shift work and risk of breast cancer in The Nurses' Health Sutudies
A partir des données des deux cohortes prospectives "The Nurses' Health Studies" incluant 78 516 puis 114 559 participantes, cette étude évalue l'association entre un travail posté de nuit et le risque de cancer du sein (durée de suivi : 24 ans ; 9 541 cas)
In 2007, the International Agency for Research on Cancer declared shift work involving circadian disruption to be a “probable” carcinogen (group 2A), noting that human evidence was limited. This study examined associations between rotating night shift work and breast cancer risk in two prospective cohorts, the Nurses’ Health Studies (NHS: 1988–2012, n = 78,516; NHS2: 1989–2013, n = 114,559), with 9,541 incident invasive breast malignancies and 24 years of follow-up. Women in NHS with 30+ years of shift work had no increased risk of breast cancer (Hazard ratio (HR) = 0.95, 95% Confidence interval (95% CI): 0.77, 1.17; Ptrend = 0.63), compared to never shift workers, though follow-up occurred primarily post-retirement from shift work. In the younger NHS2, breast cancer risk was significantly increased for women with 20+ years of shift work at baseline, reflecting young adult exposure (HR = 2.15, 95% CI: 1.23, 3.73; Ptrend = 0.23), and was marginally significantly increased for women with 20+ years of cumulative shift work, using updated exposure information (HR = 1.40, 95% CI: 1.00, 1.97; Ptrend = 0.74). In conclusion, long-term rotating night shift work was associated with increased risk of breast cancer among women who performed shift work during young adulthood. Further studies should explore the role of shift work timing on breast cancer risk.