Co-occurrence of apathy and impulse control disorders in Parkinson disease

To empirically test whether apathy and impulse control disorders (ICDs) represent independent, opposite ends of a motivational spectrum.

In this single-center, cross-sectional study, we obtained retrospective demographics and clinical data for 887 patients with idiopathic Parkinson disease (PD) seen at a tertiary care center. Mood and motivation disturbances were classified using recommended cutoff scores from self-reported measures of apathy, ICD, anxiety, and depression.

Prevalence rates included 29.0% of patients with PD with depression, 40.7% with anxiety, 41.3% with apathy, 27.6% with ICDs, and 17.0% with both apathy and ICD. The majority (61.6%) of people reporting clinically significant ICDs also reported clinically significant apathy, and more than a third of patients with apathy (41.3%) also reported elevated ICD. Anxiety and depression were highest in patients with both apathy and ≥1 ICDs. Dopamine agonist use was higher in people with only ICD compared to people with only apathy. Mood significantly interacted with demographic variables to predict motivational disturbances.

Motivational disturbances are common comorbid conditions in patients with PD. In addition, these complex behavioral syndromes interact with mood in clinically important ways that may influence the design of future clinical trials and the development of novel therapies. This study challenges the concept of apathy and ICD in PD as opposite ends of a spectrum.