Early Life Exposure to Tobacco Smoke and Ovarian Cancer Risk in Adulthood

Background: Ovarian cancer risk in adulthood may be affected by early life exposure to tobacco smoke. We investigated this relationship in two large prospective cohorts, the Nurses9 Health Study (NHS) and NHSII. Methods: In total, analyses included 110,305 NHS participants (1976–2016) and 112,859 NHSII participants (1989–2017). Self-reported early life smoking exposures were queried at baseline or follow-up questionnaires. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for risk of ovarian cancer overall and by tumor histotype. Results: Compared with women who never smoked, ovarian cancer risk was similar for women who started to smoke at age