Objective: To determine whether apathy and impulsivity co-occur in people with Huntington’s disease.

Background: Apathy and impulsivity are debilitating behavioural changes which often occur in Huntington’s disease. Once considered to be at opposite ends of a behavioural spectrum, their co-occurrence in individuals is now recognised in a number of neurological and psychiatric disorders. This suggests a shared underlying mechanism, which we recently proposed could be disruptions to the way in which rewards and costs are integrated in the brain to drive behaviour (cost-benefit decision making). However in Huntington’s disease, where both these behavioural disturbances have marked impact on people and their families, the co-occurrence of these problems has not been investigated.

Method: Carriers of the Huntington’s gene expansion (premanifest to mild manifest disease; n = 42) were recruited from two movement disorder clinics in New Zealand, along with healthy controls (n = 20). Measures of apathy (Apathy Evaluation Scale & Apathy Motivation Index) and impulsivity (Barratt Impulsiveness scale-11 & UPPS-P impulsivity scale), along with mood, cognition, clinical and quality of life measures were collected. Apathy and impulsivity measures were each reduced to a single metric per patient using principal component analysis. Pearson correlation and multiple linear regression models determined whether an association existed between apathy and impulsivity, and potential influence of other covariates.

Results: Apathy and impulsivity were correlated (r = .54, p < 0.001, [95% CI, 0.28-0.72]) in Huntington’s disease, with this association remaining after controlling for depressive symptoms, disease severity and cognitive function. Furthermore, apathy and depressive symptoms were associated with poorer quality of life, after controlling for motor disease severity and cognitive function.

Conclusion: Apathy and impulsivity co-occur in individuals with Huntington’s disease and pre-manifest gene carriers and have a significant impact on wellbeing. Their co-occurrence in HD is consistent with a shared mechanistic underpinning. Future research should focus on elucidating these mechanisms with the goal of meeting an important but unmet treatment need in this population.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/apathy-and-impulsivity-co-occur-in-huntingtons-disease/