Environmental tobacco smoke and risk of late-diagnosis incident fibroids in the Study of Women's Health across the Nation (SWAN).

OBJECTIVE: To assess the longitudinal relationship of environmental tobacco smoke (ETS) exposure during midlife, and its interaction with active smoking, with the risk of late-diagnosis incident uterine fibroids during the menopausal transition.

DESIGN: Thirteen-year prospective cohort study.

SETTING: Not applicable.

PATIENT(S): Community-based, multiracial/ethnic cohort of 2,575 women aged 42 to 52 years at baseline, undergoing the menopausal transition.

INTERVENTION(S): Questionnaire and blood draws.

MAIN OUTCOME MEASURE(S): Discrete-time proportional odds models were used to estimate the conditional odds ratio (OR) and 95% confidence interval (CI) of incident fibroids, adjusted for menopausal status, race/ethnicity, study site, age, education, estradiol levels, sex hormone use, body mass index, timing of blood draw, age at menarche, alcohol use, and smoking status and pack-years.

RESULT(S): As part of SWAN, at each near-annual study visit, ETS exposure, smoking, and fibroid occurrence were self-reported via questionnaire, and blood draws were collected. Women who were exposed to ETS (≥1 person-hour/week) had 1.28 (95% CI, 1.03, 1.60) times the adjusted odds of incident fibroids in the ensuing year compared the unexposed. The odds were elevated in never smokers (adjusted OR 1.34; 95% CI, 1.06, 1.70) and former smokers (adjusted OR 2.57; 95% CI, 1.05, 7.23).

CONCLUSION(S): In midlife, ETS exposure was associated with an increased risk of late-diagnosis incident fibroids in women undergoing the menopausal transition.