Genotype information was available for a subset of 151 patients , and for each additional repeat , patients could perform 5.6 fewer taps ( p < 0.0001 ; 95 % CI = 3.3 to 8.0 taps ) , and progressed at a faster rate of 0.45 fewer taps per year ( CAG by time interaction : p = 0.008 ; 95 % CI = 0.12 to 0.78 taps ) .