Table 1. Baseline demographics of the COHORT population by group.

	Groups that carry an expanded allele			Groups that do not carry an expanded allele
	Individuals with clinically diagnosed HD[n = 930]	First-degree relatives who pursued genetic testing and carry an expanded allele[n = 248]	First-degree relatives who did not pursue genetic testing and carry an expanded allele[n = 112]	First-degreerelatives who did not pursue genetic testing and do not carry an expanded allele[n = 224]	First-degree relatives who pursued genetic testing and do not carry an expanded allele[n = 41]	Spousesand caregivers[n = 430]	P-value*
Group definition
(CAG)n of 36 or greater	Yes	Yes	Yes	No	No	No	-
Genetic testing pursued prior to baseline	Some	Yes	No	No	Yes	No	-
Clinically diagnosed with HD	Yes	No	No	No	No	No	-
Demographics
Age [years]	51.9 (12.0)	40.9 (12.5)	40.9 (12.9)	47.2 (14.3)	43.9 (12.2)	52.4 (12.3)	<0.001
Female [%]	51.6	64.1	61.6	69.2	61.0	53.5	<0.001
White [%]	93.2	96.0	90.2	91.0	97.6	94.2	0.11
Ethnicity [% reporting Spanish origin]	3.9	4.4	1.8	4.5	4.9	4.7	0.82
Education [% completing high school or more]	89.4	90.7	88.4	93.7	73.2	90.7	0.004
Employment status [% currently in labor force]	16.8	68.6	72.3	74.4	65.9	66.5	<0.001
Marital status [% currently married]	60.2	62.1	56.3	60.1	61.0	89.5	<0.001

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.