Validation of the German version of the Dimensional Apathy Scale (G‐ <scp>DAS</scp> ): Application in amyotrophic lateral sclerosis

Apathy is a common behavioural impairment in neurodegenerative conditions and is conceptualized within the Dimensional Apathy Framework as comprising Executive, Emotional and Initiation subtypes. The Dimensional Apathy Scale (DAS) is widely used to assess these domains, yet no validated German version has been available. This study aimed to translate and validate the German DAS (G-DAS) in control participants (HC) and to characterize apathy profiles in German-speaking people with amyotrophic lateral sclerosis (pwALS). Seventy-seven HC and 32 pwALS completed self-rated and caregiver-rated measures of apathy, depression, disinhibition and executive dysfunction. The G-DAS was translated using a multi-round back-translation procedure. Psychometric validation was undertaken in the HC cohort. A subsample of HC matched to pwALS on age and sex was used for between-group comparisons and for deriving exploratory reference thresholds. The G-DAS demonstrated good to high internal consistency across subscales (α = .76-.85) and total scores (self-rated: α = .88; caregiver-rated: α = .86). Convergent validity was supported by significant correlations with the Apathy Evaluation Scale and Frontal Systems Behavior subscales, particularly for the Initiation and Executive subscales. Divergent validity was evidenced by the absence of associations with anxiety and depression. PwALS showed significantly higher Executive and Initiation apathy compared with matched HC, whereas Emotional apathy did not differ. Exploratory threshold scores derived from matched HC indicated that up to 47% of pwALS exhibited clinically elevated Initiation apathy. The G-DAS is a reliable and valid German-language measure of multidimensional apathy. It effectively captures the characteristic Executive and Initiation apathy profile in ALS, supporting its clinical and research utility.