Objective: Previous case-control studies have suggested that women with migraine have lower risk of developing breast cancer, but conflicting results were noted in cohort studies. We investigated the association between migraine and breast cancer incidence in a nationwide population-based cohort study. Methods: We identified 25,606 women with migraine between 2000 and 2013 from the National Health Insurance Research Database in Taiwan. Each migraineur was randomly frequency matched with four women without migraine by age and index year of migraine diagnosis. Cox's proportional hazard regression analysis was performed to estimate the association between migraine on the risk of developing breast cancer. Results: With a mean follow-up of 7.3 years, 234 and 978 breast malignancies occurred in the migraine cohort and matched cohort, respectively. Migraine was not associated with the risk of breast cancer (adjusted hazard ratio = 1.03, 95% confidence interval = 0.89-1.21). Among women with migraine, independent risk factors for breast cancer included older age, alcohol-related illness, and receipt of a greater number of breast cancer screening examinations, and independent protective factors included the use of antihypertensive agents, statins, and nonsteroidal anti-inflammatory drugs. Further analyses indicated that women with ≥4 medical visits for migraine per year had a significantly greater risk of breast cancer than the matched cohort. Conclusions: Migraine was not associated with a decreased risk of developing breast cancer among Taiwanese women. Further prospective studies on other geographic populations or on the association between migraine frequency and the risk of developing breast cancer are warranted to validate our findings.
Keywords: breast cancer; cohort study; epidemiology; migraine.