Risk of ischaemic stroke in patients with migraine: a longitudinal follow-up study using a national sample cohort in South Korea

OBJECTIVE: Accumulating evidence has supported the association between migraine and stroke, but the causative association remains unclear. We aimed to investigate the risks of different types of stroke in patients with migraine. DESIGN: A longitudinal follow-up study. SETTING: Data collected from a national cohort between 2002 and 2013 by the South Korea Health Insurance Review and Assessment. PARTICIPANTS: We extracted the data from patients with migraine (n=41 585) and 1:4 matched controls (n=1 66 340) and analysed the occurrence of ischaemic and haemorrhagic strokes. The migraine group included participants treated for migraine (International Classification of Disease-10 (ICD-10): G43)≥2 times. Haemorrhagic stroke (I60-I62) and ischaemic stroke (I63) were determined based on the admission histories. The crude and adjusted HRs were calculated using Cox proportional hazard models, and the 95% CI were determined. Subgroup analyses stratified by age and sex were also performed. RESULTS: Higher rates of ischaemic stroke were observed in the migraine group (2.3% [964/41,585]) than in the control group (2.0% [3294/166 340], P<0.001). The adjusted HR for ischaemic stroke was 1.18 (95% CI=1.10 to 1.26) in the migraine group (P<0.001). Compared with control subjects, participants who reported migraine with aura and migraine without aura had increased adjusted HRs of 1.44 (95% CI=1.09 to 1.89) and 1.15 (95% CI=1.06 to 1.24), respectively, for ischaemic stroke, but no increased risk of haemorrhagic stroke. In our subgroup analysis, a strong association between migraine and ischaemic stroke was observed in young patients, specifically young women. The contribution of migraine to the occurrence of ischaemic stroke was also observed in middle-aged women and old women (each P<0.05). The risk of haemorrhagic stroke did not reach statistical significance in any age group. CONCLUSION: Migraine is associated with an increased risk of ischaemic stroke, but not haemorrhagic stroke.