Should female gender be included in risk scores for stroke?

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According to a study, which was presented at the ESC annual meeting and published in the Journal of Thrombosis and Haemostasis, female gender is only a significant risk for stroke in patients with atrial fibrillation among those aged ≥75 years–indicating its inclusion in risk scores for stroke may not be required.

Anders Mikkelsen, Department of Cardiology, Copehagen University Hospital, Gentofte, Copenhagen, Denmark, and others reported in the Journal of Thrombosis and Haemostatsis that while some studies have shown that female gender is an independent risk factor for stroke in patients with atrial fibrillation, a few have not. They added, as the European Society of Cardiology now advocates using the CHA2DS2-VASc score (congestive heart failure, hypertension, age [>75 years], diabetes, prior stroke, vascular disease, age [65-74 years], and sex [female]), to assess the risk of stroke in patients with atrial fibrillation, they aimed to assess whether female sex was associated with an increased risk of stroke or thromboembolism in a large real-world population of patients with non-valvular atrial fibrillation. Mikkelsen et al wrote: “In particular, we aimed to investigate whether female sex is an independent stroke risk factor (ie, independent from other established stroke risk factors in atrial fibrillation patients) in patients aged <75 years, which should lead to antithrombotic treatment without the presence of any other additional stroke risk factors.”

The authors evaluated the incidence of stroke among patients diagnosed with non-valvular atrial fibrillation and who did not receive anticoagulation therapy between 1997 and 2008 (using national Danish registers). They subdivided patients (87,202 overall, 44,744 female) into various age groups: <65; 65–74 years; and ≥75 years. Among those under the age of 75, the rate of stroke was not increased in female patients compared with male patients. However, Mikkelsen et al reported that compared with men aged ≥75 years, “The risk [of stroke/thromboembolism] among females aged ≥75 years was increased by 10-20%”

Mikkelsen et al commented that it was unknown why women aged ≥75 years were at increased risk of stroke and that further research was needed to investigate the link between female gender and the risk of stroke. They added: “Our study suggests that female sex should not be automatically included as a stroke/thromboembolism risk factor in guidelines or in the CHA2DS2-VASc without prior consideration of ‘age <65 years and lone atrial fibrillation’ criterion.” They added that female patients aged ≥75 years would already be classified as high risk of stroke (and thus eligible for treatment with anticoagulation) as a result of their age.

However, they said that patient values and preferences should be taken into account given that stroke, as a result of atrial fibrillation, was a “devastating condition” that could be “effectively prevented by oral anticoagulation.”

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