Stroke/systemic embolism rates were consistent among older ( @ % rivaroxaban versus @ % warfarin per @ patient-years ; hazard ratio = @ ; @ % confidence interval , @-@ @ ) and younger patients ( @ % versus @ % / @ patient-years ; hazard ratio = @ ; @ % confidence interval , @-@ @ ; interaction P = @ ) , as were major bleeding rates ( @ years : @ % rivaroxaban versus @ % warfarin per @ patient-years ; hazard ratio = @ ; @ % confidence interval , @-@ @ ; < @ years : @ % versus @ % / @ patient-years ; hazard ratio = @ ; @ % confidence interval , @-@ @ ; interaction P = @ ) .