(HealthDay News) – Women with atrial fibrillation (AF) have a higher risk of ischemic stroke than men with AF, related in part to differences in the percent time in the therapeutic range (TTR) associated with warfarin anticoagulation control, according to research published in the Dec. 15 issue of The American Journal of Cardiology.

To determine the incidence of ischemic stroke by gender and the impact of TTR on the correlation between gender and ischemic stroke, Renee M. Sullivan, MD, of the University of Iowa in Iowa City, and colleagues used data from the Atrial Fibrillation Follow-up Investigation of Rhythm Management trial involving 4,060 patients with AF.

The researchers found that, compared with men, women had significantly higher congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, prior stroke, transient ischemic attack, or thromboembolism scores and more ischemic strokes compared with men (5% vs. 3%; odds ratio, 1.6). For women vs. men, significantly more time was spent outside the therapeutic range (40% vs. 37%) and below the therapeutic range (29% vs. 26%). For women, but not men, a higher TTR protected against ischemic stroke. Significantly more ischemic strokes were seen for women with a comparably high TTR (≥66%). Gender, having a TTR less than 46% vs. >80%, age, and previous stroke all correlated significantly with stroke incidence.

“The major new finding in this analysis is that a lower TTR partly explains the increased risk of stroke in women compared to men, although even after adjustment for this factor women continued to be at increased risk,” the authors write.

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