Figure 3

Change in hand tapping over time by CAG length and sex. The rate of decline is faster in patients with a greater number of repeats. This can be seen by the steeper slope in the time direction when CAG length = 60 compared to when CAG length = 37, and represents the time by CAG length interaction (p = 0.008). The female plane is parallel to the male but shifted downward, indicating that females perform fewer taps overall. Age at first visit was held constant at 35 years in this figure, and differences in the number of taps at time = 0 reflect the effect of different CAG lengths (e.g. a male with CAG length = 60 who first visits the clinical at age 35 would perform approximately 125 taps, whereas with CAG length = 37 he would perform approximately 250 taps). Graphs using a different age would simply shift the planes up or down.