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.