Reliability and validity of Italian version of the Dimensional Apathy Scale in Parkinson’s Disease

Introduction: Apathy is a non-motor symptom of Parkinson’s Disease (PD). The prevalence rate of apathy ranges from 13.9% to 70% in PD. Since an association between high level of apathy and more severe motor symptoms was reported in PD patients, the evaluation of apathy in PD could be influenced by motor disability at different stage of diseases. Recently, Dimensional Apathy Scale (DAS) has been developed to evaluate and measure apathy and its aspects in patients with neurological disorders excluding possible confounding effects of motor impairments. Objectives: The aim of the present study was to explore reliability, factor structure, divergent and convergent validity of the Italian version of the DAS (I-DAS) in non demented PD patients. Methods: To achieve this aim, we recruited 107 non-demented patients with diagnosis of idiopathic PD who underwent the I-DAS, the self-report version of the Apathy Evaluation Scale (AES), the Beck Depression Inventory-II, Parkinson Anxiety Scale (PAS) and Mini Mental State Examination (MMSE). Internal consistency, convergent and divergent validities were evaluated. Construct validity was examined by Principal Components Analysis (PCA). Results: In PD sample, the I-DAS showed high internal consistency (Cronbach’s alpha=0.871). The main score of I-DAS were 25.25 (standard deviation: 12.7) and median was 23. The correlation between I-DAS and AES were positive and moderate (r=0.539, p<0.001) indicating a good convergent validity. As for divergent validity, I-DAS scores correlated moderately with BDI-II score and poorly with the PAS and the MMSE scores, indicating good divergent validity. The IDAS showed three factorial structure similar to the original DAS. Conclusions. In conclusion, our study showed that the I-DAS had good psychometric properties in PD. Since apathy is a common non-motor symptom in neurodegenerative diseases, the I-DAS can be a valid and reliable tool to assess multidimensional apathy in PD patients.