Objective: This study investigated the association between apathy and the risk of incident Parkinson’s disease (PD) in community-dwelling adults.

Background: Apathy is a core neuropsychiatric symptom of PD. Whether apathy may be a prodromal symptom of PD is unknown.

Method: This prospective cohort study used data from 4,527 men (mean age = 77 years [range: 69-97]) from the Osteoporotic Fractures in Men Study (MrOS) and 19,082 men and women (mean age = 58 years [range: 18-96]; 65.3% female) from PPMI Online (PPMI). All participants were free from PD at baseline. Apathy at baseline was measured using the 3-item subscale of the Geriatric Depression Scale [GDS-3A]. Incident PD at follow-up was based on doctor-diagnosis. Multivariable logistic regression was used to estimate odds ratios (OR) for incident PD according to baseline apathy symptoms (none, mild, moderate, severe).

Results: In MrOS, 106 (2.4%) participants developed PD over 11.1-years of follow-up. In PPMI, 398 (2.1%) participants developed PD over 3.4-years of follow-up. After adjusting for demographic characteristics, compared with those who were free from apathy at baseline, participants with severe apathy had a 3.2-fold risk of developing PD in MrOS (OR: 3.23; 95% CI 1.64–6.37) and a 6.4-fold risk of developing PD in PPMI (OR: 6.36; 95% CI 4.61–8.78). Moreover, there was a dose–response relationship between increasing apathy severity and increasing PD risk (MrOS: P <0.001 for trend; PPMI: P <0.001 for trend). Associations between apathy and PD remained significant after adjusting for a wide range of possible confounders, and after excluding PD cases that developed within 2 years after baseline.

Conclusion: In two community-based cohorts, apathy was associated with an increased risk of developing PD, suggesting it may represent an important prodromal symptom of PD. These findings may help to identify individuals at risk of PD and could facilitate early prevention strategies.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/apathy-and-risk-of-parkinsons-disease-a-population-based-cohort-study/