Baseline motor, behavioral, and cognitive characteristics of the COHORT population by group.

Values are listed as mean (standard deviation) unless otherwise noted.COHORT = Cooperative Huntington Observational Research Trial; HD = Huntington disease; (CAG)n = cytosine-adenine-guanine repeat length in the Huntingtin allele; UHDRS = Unified Huntington's Disease Rating Scale.*P-values refer to overall tests of heterogeneity across all six groups.**For motor and behavioral measures, higher scores reflect greater impairment. For cognitive, independence, and functional measures, higher scores reflect less impairment.