Apathy in untreated early-stage Parkinson disease: relationship with other non-motor symptoms

Apathy is a frequent and disabling behavioral disorder in patients with Parkinson's disease (PD). Its prevalence in treatment-naive patients with early-stage PD has not been extensively investigated. Moreover, whether apathy is related to other non-motor symptoms in early-stage PD is unknown. Our objective was to determine the prevalence and features of apathy and associated factors in a group of treatment-naive patients with early-stage PD. Ninety-five treatment-naive patients with early-stage PD participated in the study. Apathy, depression, motor symptoms, and overall cognitive efficiency were assessed. The presence of the main non-motor symptoms was checked during a detailed clinical interview. Group comparisons were carried out to investigate the association with apathy. Eighteen patients (18.95%) were diagnosed as apathetic, and five of the latter had concomitant depression. Apathetic patients had significantly more severe motor symptoms (P < 0.001) and a lower cognitive status (P = 0.032) than non-apathetic patients. When considering non-motor symptoms, apathy was significantly associated only with fatigue (P = 0.007) and anhedonia (P = 0.010), both of which were more prevalent in apathetic patients than in non-apathetic patients. In treatment-naive patients with early-stage PD, apathy was significantly associated with more severe motor symptoms and a lower cognitive status. After adjustment for these factors, apathy appeared to be a relatively isolated, independent symptom because the only other associated non-motor symptoms were fatigue and anhedonia.