Characteristics of apathy in Parkinson's disease.

The objective of this study was to use the Lille Apathy Rating Scale to assess apathy in a large population of Parkinson's disease (PD) patients and identify several different apathy profiles. One hundred fifty-nine patients with probable PD and 58 healthy controls participated in the study. Apathy was assessed using the Lille Apathy Rating Scale. Motor, cognitive, and depressive symptoms were rated on standardized scales. Data were analyzed using linear regression and multivariate analyses of variance. Thirty-two percent of the PD patients were classified as apathetic. Apathy was more frequent in patients with dementia. The four apathy dimensions contributed differently to the overall severity of the apathetic condition. Action initiation and intellectual curiosity had a marked influence. Linear regression analysis revealed that the apathy level was mainly determined by cognitive impairment, not associated with the severity of motor symptoms, and only associated with the apathy subcomponent of the Montgomery and Asberg Depression Rating Scale. Apathy is highly prevalent in PD patients. Apathy profiles vary according to the clinical presentation of PD. The high prevalence of apathy in PD suggests the involvement of frontal-subcortical circuits. Although the neurochemical substrate of apathy remains poorly characterized, the strong link between apathy and cognitive impairment observed in several studies suggests the participation of nondopaminergic circuits.