In addition, literature review suggests that female sex as an independent risk factor of stroke is still controversial, because some studies demonstrated that the odds ratio or hazard ratio of female to male sex for thromboembolism is not significant. Indeed, the analysis of a J-RHYTHM registry revealed that female sex was not a risk for thromboembolism in the Japanese cohort. Therefore, the novel risk stratification for stroke prevention in AF patients who have CHA2DS2-VASc score of 0 or 1 in men or CHA2DS2-VASc score of 1 or 2 in female should be needed in Asian population in order to define true low risk patients in the low risk population based on the CHA2DS2-VASc scoring system.