Duration, frequency, recency, and type of migraine and the risk of ischaemic stroke in women of childbearing age.

BACKGROUND Migraine is recognised increasingly as a risk factor for ischaemic stroke in women of childbearing age. Migraine with aura poses a higher risk than migraine without aura. OBJECTIVE To investigate further the effect of duration, frequency, recency, and type of migraine on the risk of ischaemic stroke. METHODS Additional analyses of a previously reported multicentre case-control study of the relation between stroke and migraine in women aged 20-44 years. RESULTS Among 86 cases of ischaemic stroke and 214 controls, the adjusted risk of ischaemic stroke was significantly associated with: (1) migraine of more than 12 years duration, odds ratio (OR) 4.61 (1.27-16.8); (2) initial migraine with aura, OR 8.37 (2.33-30.1); (3) particularly if attacks were more frequent than 12 times per year, OR 10.4 (2.18-49.4). In no case did correction for oral contraception usage significantly alter these odds ratios. Increasing risk of ischaemic stroke was related to a change to increased frequency of headaches (trend p <or= 0.03). CONCLUSIONS These data support earlier reports of a relation between ischaemic stroke and migraine with aura. The risk seems particularly high in those whose initial migraine type involved aura occurring more than 12 times per year.