Comparison of Huntington's Disease in Europe and North America

Background: In a rare disorder such as Huntington's disease (HD), a global network of clinical trial sites with access to patients speeds up recruitment into clinical trials. The objective was to test the hypothesis that demographics, HTT genotype, clinical spectrum, and progression are similar in HD participants of two large observational HD studies, the European Huntington's Disease Network's European REGISTRY study and the North American COHORT study.

Methods: REGISTRY cross-sectional data were available from a total of 7,384 participants (1,125 [15.2%] premanifest and 6,259 [84.8%] manifest HD). COHORT cross-sectional data from 1,499 participants at 44 study sites were available (175 pre-HD [11.7%], 1,324 manifest HD [88.3%]). Participants were assessed clinically using the Unified Huntington's Disease Rating Scale (UHDRS). Longitudinal data were available for total motor score and cognitive performance in more than 50% of REGISTRY participants and more than 70% of COHORT participants.

Results: Demographics, HTT genotypes, phenotype, and progression were similar in the two studies. Patients in Europe were prescribed antidyskinetics more frequently, and antidepressants less frequently, than in North America. In either study, participants on antidyskinetic medication had higher UHDRS total motor scores, worse function assessment scores, and worse cognitive scores than those taking antidepressants or no medication. In contrast, motor, function assessment, and cognitive scores were broadly similar in participants taking antidepressants or no medication. The differences in cognitive performances between languages were small.

Conclusions: Our data suggest that HD patients, and the way they are assessed, are similar across two continents with different cultures and languages.