Migraine and the risk of stroke: an updated meta-analysis of prospective cohort studies

Dozens of observational studies and two meta-analyses have investigated the association of migraine with the risk of stroke, but their results are inconsistent. We aimed to quantitatively evaluate the relationship between migraine and stroke risk by performing a meta-analysis of prospective cohort studies. PubMed and Embase were searched through July 2016 to identify studies that met pre-stated inclusion criterion and reference lists of retrieved articles were also reviewed. Information on the characteristics of the included study, risk estimates, and control for possible confounding factors were extracted independently by two authors. The random-effects model was used to calculate the pooled risk estimates. Eleven prospective cohort studies involving 3371 patients with stroke and 2,221,888 participants were included in this systematic review. Compared with non-migraineurs, the pooled relative risks of total stroke, hemorrhagic stroke, and ischemic stroke for migraineurs were 1.55 [95% confidence interval (CI) 1.38-1.75], 1.15 (95% CI 0.85-1.56), and 1.64 (95% CI 1.22-2.20), respectively. Exception of any single study did not materially alter the combined risk estimate. Integrated epidemiological evidence supports that migraine should be associated with the increased risk of total stroke and ischemic stroke, but the relationship between migraine and the risk of hemorrhagic stroke is not of certainty.