Objective: To compare differences in the mean cognitive impairment (CI) of patients with and without clinically significant apathy in PD, PD-mild cognitive impairment (PD-MCI), and PD-dementia (PDD), controlling for the effects of depression.

Background: Apathy, characterized by reduced interest and motivation, is common in PD. Apathy emerges as a correlate and predictor of CI, specifically in executive functioning domains. To our knowledge, no previous studies have investigated the effect of disease stage (i.e., PD, PD-MCI, PDD) on the apathy-CI relationship, controlling for depression.

Method: Multi-site datasets were combined through collaboration and data-sharing agreements. Patients were classified as having clinically significant apathy and/or depression using questionnaire measures. PD patients on dopaminergic therapy performed the Montreal Cognitive Assessment (MoCA). ANCOVA was used to test the main effect of apathy, as well as the disease stage x apathy interaction on CI. Depression, sex, education, and age were included as covariates.

Results: In 442 PD patients (PD = 289, PD-MCI = 98, and PDD = 55), 45 participants met criteria for apathy, 134 met criteria for depression, and 55 participants met criteria for both. ANCOVA revealed a significant main effect of apathy on MoCA total scores when depression was included as a covariate, F(1, 440) = 6.26, p = .01, η_p² = .01. A significant apathy x disease stage interaction was found on the visuospatial/executive (VSE) subdomain of the MoCA, F(2, 317) = 4.22, p = .02, η_p² = .03. Patients with PDD and apathy were severely impaired on the VSE domain compared to patients with PDD without apathy.

Conclusion: The findings of this study suggest that apathy has an impact on cognitive performance distinct from that of depression. Additionally, the findings suggest that apathy can produce selective impairments in specific cognitive domains based on disease stage. Future analyses should include measures of motor disease severity and levodopa equivalent daily dosage. This study provides insight into the effect of psychiatric symptoms on patients at-risk for CI in PD.

References: Sockeel, P., Dujardin, K., Devos, D., Denève, C., Destée, A., & Defebvre, L. (2006). The Lille apathy rating scale (LARS), a new instrument for detecting and quantifying apathy: Validation in Parkinson’s disease. Journal of Neurology, Neurosurgery, and Psychiatry, 77(5), 579–584. https://doi.org/10.1136/jnnp.2005.075929

Béreau, M., Van Waes, V., Servant, M., Magnin, E., Tatu, L., & Anheim, M. (2023). Apathy in Parkinson’s Disease: Clinical Patterns and Neurobiological Basis. Cells, 12(12), 1599. https://doi.org/10.3390/cells12121599

Dujardin, K., Sockeel, P., Delliaux, M., Destée, A., & Defebvre, L. (2009). Apathy may herald cognitive decline and dementia in Parkinson’s disease: Apathy in Parkinson’s Disease. Movement Disorders, 24(16), 2391–2397. https://doi.org/10.1002/mds.22843

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MDS Abstracts - https://www.mdsabstracts.org/abstract/apathy-produces-selective-deficits-in-cognitive-function-when-controlling-for-depression-in-patients-with-parkinsons-disease/