This study population included a total of 116,110 and 113,974 female registered nurses who were recruited 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. Multivariable-adjusted Cox regression analyses were performed to estimate age- and multivariable-adjusted incidence risk ratio (IRR) and 95% confidence intervals (CIs) of bladder cancer. The authors used inverse-variance-weighted meta-analysis to pool estimates across cohorts.
During a median 29 years of follow-up (IQR 23.9-35.9), 629 incident bladder cancer cases were confirmed. In the NHS, 22,566 (21.3%) women were menopausal at baseline, compared to 2,723 women (2.4%) in the NHSII. Among women in NHS, compared to those with menopause onset at age 50+, younger age at menopause (≤45) was associated with an increased risk of bladder cancer (MV-IRR 1.41, 95%CI 1.11-1.81, Ptrend=0.01), particularly among ever smokers (IRR for age at menopause ≤45: 1.53, 95%CI: 1.15-2.04; PInteraction=0.16). Neither, age at menarche, nor parity, age at first birth, oral contraceptive use, or postmenopausal hormone use were associated with BCa risk.
The full results of the analysis are as follows:
This is a well performed epidemiological, hypothesis-generating study demonstrating an association between earlier menopause and risk of bladder cancer. Future-directed studies further elucidating the nature of this risk factor will be important.
The authors concluded their study noting that earlier age at menopause was associated with a higher risk of bladder cancer, which is notable primarily in smokers, highlighting the importance of counseling regarding smoking cessation in women. The potential protective impact of longer reproductive years on bladder cancer risk adds new evidence to our understanding of sexual dimorphism in bladder.
Presented by: Mohammad Abufaraj, Medical University of Vienna, Vienna, Austria
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