An exploration of apathy and impulsivity in Parkinson disease

Background. Apathy and impulsivity in Parkinson disease (PD) are associated with clinically significant behavioral disorders. Aim. To explore the phenomenology, distribution, and clinical correlates of these two behaviors. Methods. In PD participants (n = 99) without dementia we explored the distribution of measures of motivation and impulsivity using univariate methods. We then undertook factor analysis to define specific underlying dimensions of apathy and impulsivity. Regression models were developed to determine the associated demographic and clinical features of the derived dimensions. Results. The factor analysis of apathy (AES-C) revealed a two-factor solution: "cognitive-behavior" and "social indifference". The factor analysis of impulsivity (BIS-11) revealed a five-factor solution: "inattention"; "impetuosity"; "personal security"; "planning"; and "future orientation". Apathy was significantly associated with: age, age of motor symptom onset (positive correlation), disease stage, motor symptom severity, and depression. Impulsivity was significantly associated with: age of motor symptom onset (negative correlation), gambling and anxiety scores, and motor complications. We observed an overlap of apathy and impulsivity in some participants. Conclusion. In PD, apathy and impulsivity have specific phenomenological profiles and are associated with particular clinical phenotypes. In spite of this, there is some overlap of behaviors which may suggests common aspects in the pathology underlying motivation and reward processes.