In the lower disease severity subgroup , there were fewer falls in the exercise group compared with controls ( IRR = 0.31 , 95 % CI 0.15-0 .62 , p < 0.001 ) , while in the higher disease severity subgroup , there was a trend toward more falls in the exercise group ( IRR = 1.61 , 95 % CI 0.86-3 .03 , p = 0.13 ) .