Early menopause is associated with a higher risk of bladder cancer (BCa), primarily in smokers, according to research presented at the European Association of Urology 2019 conference in Barcelona, Spain at the weekend.
The study population comprised a total of 106,138 and 113,974 female-registered nurses participating in the Nurses' Health Study (NHS) and NHS II, respectively. Reproductive and hormonal factors, smoking history and other relevant data were recorded in biennial self-administered questionnaires.
During up to 36 years of follow-up, 441 incident BCa cases were confirmed. In the NHS, 22,566 (21.3%) women were menopausal at baseline, compared with 2,723 women (2.4%) in the NHSII. Among women in the NHS, compared with those with menopause onset at age 50+, younger age at menopause (trend=.01), particularly among ever smokers (IRR for age at menopause Interaction=.16).
Age at menarche, parity, age at first birth, oral contraceptive use and post-menopausal hormone use were not associated with BCa risk.
The potential protective impact of longer reproductive years on BCa risk adds new evidence to the understanding of sexual dimorphism in BCa.