Background: Apathy, often-unrecognized in Parkinson's Disease (PD), adversely impacts quality-of-life (QOL) and may increase with disease severity. Identifying apathy early can aid treatment and enhance prognoses. Whether feelings related to apathy (e.g., loss of pleasure) are present in mild PD and how apathy and related feelings increase with disease severity is unknown.
Methods: 120 individuals (M age: 69.0 ± 8.2 y) with mild (stages 1-2, n = 71) and moderate (stages 2.5-4; n = 49) PD were assessed for apathy and apathy-related constructs including loss of pleasure, energy, interest in people or activities, and sex. Correlations were used to determine the association of apathy with apathy-related constructs. Regression models, adjusted for age, cognitive status, and transportation, compared groups for prevalence of apathy and apathy-related feelings.
Results: Apathy-related constructs and apathy were significantly correlated. Apathy was present in one in five participants with mild PD and doubled in participants with moderate PD. Except for loss of energy, apathy-related constructs were observed in mild PD at a prevalence of 41% or greater. Strong associations were noted between all apathy-related constructs and greater disease severity. After adjustment for transportation status serving as a proxy for independence, stage of disease remained significant only for loss of pleasure and loss of energy.
Conclusion: People with mild PD showed signs of apathy and apathy-related feelings. Loss of pleasure and energy are apathy-related feelings impacted by disease severity. Clinicians should consider evaluating for feelings related to apathy to enhance early diagnosis in individuals who might otherwise not exhibit psychopathology.
Keywords: Hoehn and Yahr Scale; Parkinson’s disease; apathy; neuropsychiatric symptoms; non-motor symptoms; quality-of-life.