Increased risk of bell palsy in patients with migraine: A nationwide cohort study

Objective: To evaluate the association between migraine and Bell palsy and to examine the effects of age, sex, migraine subtype, and comorbid risk factors for Bell palsy. Methods: This nationwide cohort study was conducted using data from the Taiwan National Health Insurance Research Database. Subjects aged 18 years or older with neurologistdiagnosed migraine from 2005 to 2009 were included. A nonheadache age- and propensity score-matched control cohort was selected for comparison. All subjects were followed until the end of 2010, death, or the occurrence of a Bell palsy event. Cox proportional hazards regression was used to calculate the adjusted hazard ratios and 95% confidence intervals to compare the risk of Bell palsy between groups. Results: Both cohorts (n = 136,704 each) were followed for a mean of 3.2 years. During the follow-up period, 671 patients (424,372 person-years) in the migraine cohort and 365 matched control subjects (438,677 person-years) were newly diagnosed with Bell palsy (incidence rates, 158.1 and 83.2/100,000 person-years, respectively). The adjusted hazard ratio for Bell palsy was 1.91 (95% confidence interval, 1.68-2.17; p <0.001). The association between migraine and Bell palsy remained significant in sensitivity analyses, and tests of interaction failed to reach significance in all subgroup analyses. Conclusion: Migraine is a previously unidentified risk factor for Bell palsy. The association between these 2 conditions suggests a linked disease mechanism, which is worthy of further exploration.