Trans fat, aspirin, and ischemic stroke in postmenopausal women.

Objective: To examine the associations between dietary fat intake and ischemic stroke among postmenopausal women.

Methods: We conducted a prospective cohort study of 87,025 generally healthy postmenopausal women (age, 50-79 years) enrolled in the Women's Health Initiative Observational Study. Repeated and validated dietary assessments were done using a self-administered food frequency questionnaire. We used Cox proportional hazards models to estimate hazard ratios (HRs) of ischemic stroke based on quintiles of the cumulative average of fat intake.

Results: We documented 1,049 incident cases of ischemic stroke over 663,041 person-years of follow-up. Women in the highest quintile of trans fat intake had a significantly higher incidence of ischemic stroke (HR, 1.39; 95% confidence interval [CI], 1.08-1.79; p-trend = 0.048) compared with women in the lowest quintile, while controlling for multiple covariates. The observed association was modified by aspirin use (p-interaction = 0.02). The HR was 1.66 (95% CI, 1.21-2.36; p-trend < 0.01) among baseline non-aspirin users (n = 67,288) and 0.95 (95% CI, 0.60-1.48; p-trend = 0.43) among aspirin users (n = 19,736). No significant associations were found between intakes of saturated, monounsaturated, or polyunsaturated fat and ischemic stroke or any ischemic stroke subtypes.

Interpretation: In this large cohort of postmenopausal women, higher intake of trans fat was associated with incident ischemic stroke independent of major lifestyle/dietary factors. Aspirin use may attenuate the potential adverse effect of trans fat intake on ischemic stroke.