Women with atrial fibrillation who are not on anticoagulant therapy have a higher rate of ischemic stroke and face a higher absolute risk for stroke than do men with the condition, according to a joint study by researchers at the University of California, San Francisco, Massachusetts General Hospital, the Division of Research at Kaiser Permanente and Boston University School of Medicine.
Using a sample of 13,559 patients with atrial fibrillation, or rapid irregular contractions of the heart, researchers compared the rates of ischemic stroke between men and women and examined the efficacy and complications associated with a common blood thinner, Warfarin. Their findings are being reported in the September 20 issue of Circulation.
Warfarin is well known to be effective in reducing the risk of stroke in persons with atrial fibrillation; however prior studies have provided conflicting evidence about whether women with atrial fibrillation have a higher risk for stroke than men when not taking blood thinners. "The research from this study clearly shows that gender plays a role in ischemic stroke risk and occurrence," said lead author Margaret Fang, MD, MPH, assistant adjunct professor of medicine, and hospitalist at UCSF Medical Center.
The higher incidence of stroke in women not taking Warfarin therapy occurred among women in all stroke-risk-factor categories, including those with prior stroke, hypertension, congestive heart failure, coronary artery disease and diabetes. Because of the significant differences in the rate of stroke between men and women, the study indicates that being a woman is an independent risk factor for stroke and should be considered when choosing treatment options for women with atrial fibrillation.
According to the researchers, atrial fibrillation is the most common cardiac arrhythmia, and a major risk factor for both ischemic stroke and peripheral embolism, an obstruction of the blood supply to an organ. Anticoagulation therapies, such as Warfarin, are well known to substantially reduce the risk of atrial fibrillation-related stroke and embolism, but also have been shown to increase the risk for hemorrhage. "Because of this increased hemorrhage risk, physicians are sometimes hesitant to prescribe the drug, and some studies have shown that women are less likely to receive warfarin therapy than men," Fang said. "However, we found that women in our study did not suffer bleeding complications related to Warfarin more often than men who were using the therapy."
Furthermore, data showed that women may actually benefit more from Warfarin because of their higher baseline risk for stroke. "Women with atrial fibrillation, particularly those with other risk factors for stroke, should be especially encouraged to take Warfarin," Fang added.
The researchers used data from Kaiser Permanente's AnTicoagulation and Risk Factors In Atrial Fibrillation (ATRIA) Study cohort. The study was supported by a Public Health Services research grant from the National Institutes on Aging and the Eliot B. and Edith C. Shoolman Fund of Massachusetts General Hospital.
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