Reproductive factors, exogenous hormone use and bladder cancer risk in a prospective study.

Sex is a consistent predictor of bladder cancer: men experience 2-4-fold higher age-adjusted rates than women in the U.S. and Europe. The objective of this study was to examine whether hormone-related factors are associated with bladder cancer in women. We examined parity, age at menarche, age at first birth, age at menopause, oral contraceptive use and menopausal hormone therapy (HT) use and bladder cancer risk in the Breast Cancer Detection Demonstration Project Follow-Up Study. Endpoint and exposure information was collected on 54,308 women, using annual telephone interviews (1980-86) and 3 mailed, self-administered questionnaires (1987-98). During an average follow-up time of 15.3 years, 167 cases of bladder cancer were identified. Univariate and adjusted rate ratios (RRs) were estimated using Poisson regression. Parity, age at menarche, age at first birth, age at menopause, and oral contraceptive use were not associated with bladder cancer risk. The majority of menopausal women who took HT used estrogen therapy (ET). Postmenopausal women with less than 4 years, 4-9 years, 10-19 years and 20 or more years of ET use had RRs of 1.55 (95% CI = 0.96-2.51), 1.00 (95% CI = 0.49-2.04), 1.23 (95% CI = 0.62-2.43) and 0.57 (95% CI = 0.14-2.34), respectively, compared with nonusers (p = 0.50). Findings from this study are not consistent with the hypothesis that hormone-related factors in women are associated with bladder cancer.