Migraine and risk of haemorrhagic stroke in women: prospective cohort study.

OBJECTIVES: To examine the association between migraine and migraine aura status with risk of haemorrhagic stroke.

DESIGN: Prospective cohort study.

SETTING: Women's Health Study, United States.

PARTICIPANTS: 27,860 women aged >or=45 who were free from stroke or other major disease at baseline and had provided information on self reported migraine, aura status, and lipid values.

MAIN OUTCOME MEASURES: Time to first haemorrhagic stroke and subtypes of haemorrhagic stroke.

RESULTS: At baseline, 5130 (18%) women reported any history of migraine; of the 3612 with active migraine (migraine in the previous year), 1435 (40%) described having aura. During a mean of 13.6 years of follow-up, 85 haemorrhagic strokes were confirmed after review of medical records. Compared with women without a history of migraine, there was no increased risk of haemorrhagic stroke in those who reported any history of migraine (adjusted hazard ratio 0.98, 95% confidence interval 0.56 to 1.71, P=0.93). In contrast, risk was increased in women with active migraine with aura (2.25, 1.11 to 4.54, P=0.024). The age adjusted increased risk was stronger for intracerebral haemorrhage (2.78, 1.09 to 7.07, P=0.032) and for fatal events (3.56, 1.23 to 10.31, P=0.02). Four additional haemorrhagic stroke events were attributable to migraine with aura per 10 000 women per year. Women who reported active migraine without aura had no increased risk for haemorrhagic stroke.

CONCLUSION: Migraine with aura might, in addition to ischaemic events, also be a risk factor for haemorrhagic stroke. The relatively low number of events and attributable risk should caution against definitive conclusions and call for further confirmation of these observations.