Dimensions of apathy in Parkinson's disease: exploratory factor analysis of the apathy scale.

Apathy, an intrinsic disorder of motivation, can manifest in cognitive, affective, and behavioral domains. Recent attempts to formalize diagnostic criteria for apathy have advocated this triadic structure. The Apathy Scale (AS) is the only recommended measure for assessing apathy in Parkinson's disease (PD) by a Movement Disorders task force. We tested the hypothesis that the AS distinctly measures the three proposed domains of apathy in PD. Participants were 226 non-demented PD patients. Apathy Scale data were examined with exploratory factor analysis (EFA). The three factor solution resembled the triadic structure of cognitive, behavioral, and affective domains; however, adjustments to the AS may be appropriate.