Risk of ischemic stroke and utility of CHA(2)DS(2)‐VASc score in women and men with atrial fibrillation

BACKGROUND: The magnitude of increased risk of stroke in women with atrial fibrillation (AF) remains uncertain. HYPOTHESIS: We investigated the risk of ischemic stroke and death in women and men with AF, and the risk associated with individual non‐sex CHA(2)DS(2)‐VASc risk factors. METHODS: Retrospective cohort study of 231 077 (48.1% women) nonselected patients with AF not receiving oral anticoagulation from 2006 to 2014. Data from cross‐linked national Swedish registers. The outcome was the first occurrence of ischemic stroke or death. Median age was 82 and 75 years in women and men, respectively. Mean follow‐up was 2.5 years. RESULTS: Hazard ratios, adjusted for non‐sex CHA(2)DS(2)‐VASc risk factors, for women vs men were 1.53, 95% CI: 1.49‐1.58 for ischemic stroke and 1.24, 95% CI: 1.22‐1.26 for death, respectively. When divided into age groups the differences in ischemic stroke rates between women and men were attenuated. In patients with only one non‐sex CHA(2)DS(2)‐VASc risk factor allotted 1 point, ischemic stroke rates per 100 person‐years were 1.22 in women (n = 9838) and 1.02 in men (n = 15 609), respectively, P < .006. In both women and men, age of 65 to 74 years was associated with higher ischemic stroke risk compared to other non‐sex CHA(2)DS(2)‐VASc risk factors allotted 1 point. CONCLUSIONS: The risk of ischemic stroke was 1.5‐fold higher in women compared to men but this association appears to be the result of confounding by age. In the low risk end, the CHA(2)DS(2)‐VASc risk score underestimates the ischemic stroke risk conferred by age 65 to 74 years, while it overestimates the risk conferred by female sex.