Objective: Our overall goal was to learn whether apathy would be associated with autonomic symptoms in Parkinson’s disease (PD). We examined whether a) PD patients with clinically-significant apathy report more total autonomic symptoms than non-apathetic PD patients and b) specific autonomic symptoms (e.g., gastrointestinal, thermoregulatory) are differentially associated with apathy.

Background: Apathy is a prevalent behavioral syndrome linked to worse quality of life in PD. From a treatment perspective, one important question is how apathy relates to other non-motor clusters, including autonomic symptoms which affect ~50-80% of PD patients. To date, there have been limited studies examining the relationship between these two domains in PD; however, given a potential overlap in neural substrates and neurotransmitters (e.g., monoaminergic systems), we hypothesized elevated apathy would relate to greater autonomic load.

Method: Participants included 74 individuals (mean age=67.5+8.3 years) with PD. Autonomic symptoms were measured using the Scales for Outcomes in Parkinson’s Disease-Autonomic Dysfunction (SCOPA-AUT), consisting of a total score and 6 subdomain scores. Apathy was measured using the Apathy Scale, with cutoff of 14 to classify individuals as apathetic vs non-apathetic. Independent t-tests and Mann Whitney U Tests examined between-group differences in autonomic functioning. For those with available motor severity data (N=65), the Unified Parkinson’s Disease Rating Scale Motor Examination (UPDRS-Part III) was included as a covariate in an ANCOVA of SCOPA-AUT Total by apathy group.

Results: There were 47 (63.5%) individuals in the non-apathetic group and 27 (36.5%) individuals in the apathetic group. The apathetic group had significantly higher scores on the SCOPA-AUT Total than the non-apathetic group, t(72)=-3.52, p<.001; motor severity was not related to SCOPA-AUT Total, F(1,62)=0.11, p=.737. For specific autonomic clusters, gastrointestinal (U=892.5, p=.004) and urinary (U=870.0, p=.004) were higher in the apathetic group; other subdomains did not differ (thermoregulatory, cardiovascular, pupillomotor, sexual; all ps>.05).

Conclusion: Our study suggests autonomic symptoms, particularly gastrointestinal/urinary, are associated with apathy in PD. Future work should examine the specific mechanisms underlying these relationships, as well as if therapeutics targeting autonomic symptoms could lead to improvements in apathy (or vice versa).

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MDS Abstracts - https://www.mdsabstracts.org/abstract/apathy-in-parkinsons-disease-relation-to-autonomic-symptoms/