In elderly patients , the principal safety outcome occurred at 25.05 % / year with rivaroxaban vs. 16.95 % / year on warfarin ( hazard ratio [ HR ] , 1.49 ; 95 % confidence interval [ CI ] : 1.02-2 .16 ) , whereas the primary efficacy endpoint occurred at 2.18 % / year vs. 4.25 % / year ( HR , 0.51 ; 95 % CI : 0.20-1 .27 ) , respectively .