Stroke risk in atrial fibrillation is assessed by using the CHA2DS2-VASc score. Sex category (Sc, ie, female sex) confers 1 point on CHA2DS2-VASc. We hypothesized that female sex is a stroke risk modifier, rather than an overall risk factor, when added to a CHA2DS2-VA (sex-independent thromboembolism risk) score scale.