Objective: 1-Comparing the risk of prodromal PD between AO exposed veterans (AOEV) and non-AO exposed veterans without PD (Controls) in a Veterans Affairs (VA) hospital neurology clinic. 2-Comparing the clinical characteristics of probable prodromal PD (ppPD) to PD and Controls.

Background: AO exposure increases the risk of PD. In prodromal PD, non-motor and early motor symptoms of PD are present, but motor impairment is not enough to confirm the clinical diagnosis of PD.

Method: A convenience sample of 144 participants (all men, at least 65 years old) from a VA hospital neurology outpatient clinic participated in a biomarker study and underwent testing using MDS-UPDRS, MoCA, and questionnaires on non-motor features of PD. AOEV without PD were recruited from Vietnam veterans who were on AO benefits from the VA. The total likelihood ratio for probable prodromal PD for AOEV and Controls was calculated using the “Prodromal PD Calculator” on the MDS website (Heinzel et al. Update of the MDS Research Criteria for Prodromal PD. Mov Disord 2019). Estimated probability of ≥80% was required for classification as ppPD.

Results: No Control participant (n=30, median age=71.5 years) was classified as ppPD, whereas 15 of 54 AOEV participants (median age=76) were classified as ppPD (p<0.001).. Comparison of the ppPD (n=15, median age=74) to Controls (expanded to n=69 with addition of AOEV without ppPD or PD, median age 75) showed no difference in age, MoCA, MDS-UPDRS Parts II (motor experiences of daily living), and III (motor examination), but worse (p<0.05) scores in the Geriatric Depression Scale (GDS), MDS-UPDRS  Part I (non-motor experiences of daily living), and PD Sleep Scale-2 (PDSS-2). Comparison of the ppPD to PD (n=60, median age=75, median Hoehn-Yahr stage=2) showed no difference in age, MoCA, GDS, PDSS-2, and MDS-UPDRS Part I, but better (p<0.05) scores in MDS-UPDRS Parts II and III.

Conclusion: Exposure to AO increases the risk of prodromal PD in veterans. Consistent with expectations, the ppPD group had worse non-motor symptoms compared to Controls but without worse motor function, and had better motor function compared to PD but with similar non-motor symptoms. Veterans with AO exposure represent an enriched population for prodromal PD and could be considered as a target population to test the effects of potential neuroprotective treatments early in the course of PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/prodromal-parkinsons-disease-in-agent-orange-exposed-us-vietnam-veterans/