A recent large, international multicenter study has shown that impaired renal function is a strong predictor of stroke and systemic embolism in patients with non-valvular atrial fibrillation at moderate to high risk of stroke. The risk stratification for stroke risk in patients with non-valvular atrial fibrillation should include renal function. The study was published online December 3, 2012 in the journal Circulation. The study was designed to assess factors associated with stroke occurrence and systemic embolism. A total of 14,264 patients with nonvalvular atrial fibrillation and creatinine clearance ≥30 mL/min were randomized to receive rivaroxaban or adjusted-dose warfarin in the randomized, double-blind study of rivaroxaban atrial fibrillation stroke prevention. A proportional risk model was used to identify randomized independent correlates of the occurrence of stroke or noncentral nervous system embolism on the basis of an intention-to-treat analysis. Risk scores were derived in the cohort and validated in the cohort (an independent cohort of patients in the AF group).