Natural history of Huntington disease.

IMPORTANCE: Understanding the natural history of Huntington disease will inform patients and clinicians on the disease course and researchers on the design of clinical trials.

OBJECTIVE: To determine the longitudinal change in clinical features among individuals with Huntington disease compared with controls.

DESIGN, SETTING, AND PARTICIPANTS: Prospective, longitudinal cohort study at 44 research sites in Australia (n = 2), Canada (n =4), and the United States (n = 38). Three hundred thirty-four individuals with clinically manifest Huntington disease who had at least 3 years of annually accrued longitudinal data and 142 controls consisting of caregivers and spouses who had no genetic risk of Huntington disease.

MAIN OUTCOMES AND MEASURES: Change in movement, cognition, behavior, and function as measured by the Unified Huntington's Disease Rating Scale, the Mini-Mental State Examination, and vital signs.

RESULTS: Total motor score worsened by 3.0 points (95% CI, 2.5-3.4) per year and chorea worsened by 0.3 point per year (95% CI, 0.1-0.5). Cognition declined by 0.7 point (95% CI, 0.6-0.8) per year on the Mini-Mental State Examination. Behavior, as measured by the product of frequency and severity score on the Unified Huntington's Disease Rating Scale, worsened by 0.6 point per year (95% CI, 0.0-1.2). Total functional capacity declined by 0.6 point per year (95% CI, 0.5-0.7). Compared with controls, baseline body mass index was lower in those with Huntington disease (25.8 vs 28.8; P < .001), and average pulse was higher (74.2 vs 69.6 beats/min; P < .001).

CONCLUSIONS AND RELEVANCE: Over 3 years, the cardinal features of Huntington disease all declined in a monotonic manner. These data quantify the natural history of the disease and may inform the design of trials aimed at reducing its burden.

TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00313495.