Baseline clinical characteristics and genetics 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.
†For participants who do not carry an expanded allele, the (CAG)n of the shorter allele represents the average of two normal alleles.