Stroke/systemic embolism rates were consistent among older ( 2.29 % rivaroxaban versus 2.85 % warfarin per 100 patient-years ; hazard ratio = 0.80 ; 95 % confidence interval , 0.63-1 .02 ) and younger patients ( 2.00 % versus 2.10 % / 100 patient-years ; hazard ratio = 0.95 ; 95 % confidence interval , 0.76-1 .19 ; interaction P = 0.313 ) , as were major bleeding rates ( 75 years : 4.86 % rivaroxaban versus 4.40 % warfarin per 100 patient-years ; hazard ratio = 1.11 ; 95 % confidence interval , 0.92-1 .34 ; < 75 years : 2.69 % versus 2.79 % / 100 patient-years ; hazard ratio = 0.96 ; 95 % confidence interval , 0.78-1 .19 ; interaction P = 0.336 ) .