Dimensional Apathy as a Predictor of Health-Related Quality of Life in Parkinson's Disease

Apathy, defined as diminished self-initiated purposeful behavior, is common in Parkinson's disease (PD) and affects health-related quality of life (HRQoL). Although apathy is now recognized as a multidimensional syndrome, the contributions of total apathy and its dimensions to HRQoL, when mood and cognition are accounted for, remain unclear. The authors examined these relationships for individuals with PD.

Twenty-eight adults with PD without dementia completed the Dimensional Apathy Scale (DAS), General Anxiety Disorder-7 (GAD-7), Beck Depression Inventory-II (BDI-II), Parkinson's Disease Questionnaire-39, and a neuropsychological battery. Motor severity was assessed via the Movement Disorders Society-Unified Parkinson's Disease Rating Scale part III (MDS-UPDRS III). A cognitive composite score reflected mean within-individual performance across cognitive tests. Hierarchical regression analyses were conducted to identify predictors of HRQoL.

GAD-7, BDI-II, MDS-UPDRS III, and cognitive composite scores explained 61% of the variance in HRQoL (R²=0.605, p<0.001). Adding the DAS total score to the analysis accounted for an additional 9% of the variance (ΔR²=0.088, p=0.026), with greater apathy being associated with lower HRQoL (β=0.369, p=0.026). Secondary analyses revealed that this effect was driven exclusively by the DAS executive subdomain.

Total apathy and executive apathy have distinct negative effects on HRQoL in PD when mood and cognition are controlled for in analyses. These findings highlight the importance of assessing apathy subdomains in the setting of PD.