Abstract
BACKGROUND: Migraine with aura (MA) has been associated with increased risk of cardiovascular disease (CVD). The role of aspirin on this association remains unclear. METHODS: Post-hoc subgroup analyses of the Women's Health Study, a randomized trial testing 100 mg aspirin on alternate days in primary prevention of CVD among 39,876 women aged ≥ 45. RESULTS: During 10 years, 998 major CVD events were confirmed in 39,757 women with complete migraine information. Aspirin reduced risk of ischaemic stroke (relative risk, RR, 0.76, 95% CI 0.63-0.93) but not other CVD. Migraine or MA did not modify the effect of aspirin on CVD except for myocardial infarction (MI) (p for interaction = 0.01). Women with MA on aspirin had increased risk of MI (RR 3.72, 95% CI 1.39-9.95). Further exploratory analyses indicate that this increased risk is only apparent among women with MA on aspirin who ever smoked or had history of hypertension (p for interaction<0.01). CONCLUSIONS: In post-hoc subgroup analyses, aspirin had similar protective effects on ischaemic stroke for women with or without migraine. By contrast, our data suggest that women with MA on aspirin had increased risk of MI. The small number of outcome events in subgroups, the exploratory nature of our analyses, and lack of plausible mechanisms raise the possibility of a chance finding, which must caution the interpretation.