Differential impact of behavioral, social, and emotional apathy on Parkinson's disease

Abstract

Apathy is highly prevalent in Parkinson's disease. New findings suggest the syndrome is multifaceted. Here, we investigate whether all aspects of apathy are equally affected in Parkinson's disease and whether different dimensions of apathy were associated with depression and anhedonia. On the Apathy Motivation Index, while behavioral apathy and social apathy were elevated, emotional motivation was relatively preserved in Parkinson's disease, although a few patients did show impaired emotional sensitivity. Behavioral and social, but not emotional, apathy was associated with depression and anhedonia. These findings suggest aspects of motivation can be selectively impaired in Parkinson's disease and may have implications for guiding treatment.

Figure 1

Apathy Motivation Index findings in Parkinson's disease. (A) There was a significant positive correlation between the AMI and LARS, an established clinical interview measure of apathy. (B) An ROC curve analysis performed by adopting the LARS as the gold standard found that the AMI has good diagnostic accuracy for clinical apathy. (C) PD patients exhibited significantly greater levels of behavioral and social apathy compared to age‐matched healthy controls, but there was no significant difference in emotional apathy between the two groups. (D) Behavioral activation (BA) and social motivation (SM) correlated positively with Geriatric Depression Scale‐15 (GDS) score in both PD and controls, indicating that individuals who were more behaviorally and socially apathetic were more likely to be depressed. Emotional sensitivity (ES), however, did not correlate with depression in PD but correlated negatively in controls. Comparison of correlation coefficients between patients and controls via Fisher's r‐to‐z transformation confirmed there was a significant difference between ES and depression, but not BA and SM. (E) BA and SM correlated negatively with Snaith–Hamilton Pleasure Scale (SHAPS) in PD: Patients who were behaviorally and socially more apathetic tended to be more anhedonic. However, there was no relationship with ES. In controls, only social apathy exhibited a significant correlation with anhedonia. Fisher's transformation showed no significant differences between patients and controls in correlation between anhedonia and the three apathy subscales. AMI, Apathy Motivation Index; LARS, Lille Apathy Rating Scale. *: p<0.05; **: p<0.01; ***: p<0.001