Objective: To evaluate the clinical outcomes associated with pesticide exposure in Parkinson’s disease (PD) participants in the Canadian Open Parkinson Network (COPN)(1).

Background: Pesticide exposure has been linked to an increased risk of PD(2), but evidence on its impact on disease severity is limited. This study explores the association between pesticide exposure and clinical outcomes in PD using a Propensity score matching (PSM) analysis. To our knowledge, it is the largest study of its kind.

Method: Clinical outcomes of pesticide exposed (EPD) and non-exposed PD (NEPD) participants from the COPN cohort were analyzed. PSM was used to adjust for confounders: age, sex, disease duration, Hoehn & Yahr, education, levodopa equivalent dose, living environment, and history of working or living on a farm. Only patients with complete covariate data were included for matching. Nearest-neighbor matching (1:1, caliper=0.1) was applied.  Clinical outcomes were compared between EPD and NEPD groups, including age at onset (AAO), MDS-UPDRS subscales, and motor and non-motor symptoms. Analysis of covariance was used for continuous variables and multivariable logistic regression to determine the adjusted odds ratios (ORs) for categorical variables.

Results: A total of 1036 PD participants were matched into EPD and NEPD groups (Tab. 1-2, Fig. 1) from a sample of 1150 eligible participants. Regression analysis revealed significant differences in AAO (adjusted means: 57.3 (EPD) vs. 58.0 (NEPD), p < 0.05), MDS-UPDRS sub-scores for tremor (8.15 vs. 7.49, p < 0.05), and postural instability/gait difficulty (2.70 vs. 3.14, p < 0.05). Pesticide exposure was associated with an increased risk of reporting dyskinesias (OR: 1.58 [1.2, 2.09], p = 0.001), a tremor-dominant phenotype (OR: 1.6 [1.2, 2.12], p = 0.001), and a higher likelihood of reporting REM Behavior Disorder (RBD) (OR: 1.5 [1.16, 1.94], p = 0.002), hyposmia/anosmia (OR: 1.42 [1.11, 1.83], p = 0.006), pain (OR: 1.37 [1.04, 1.81], p = 0.03), and restless legs syndrome (OR: 1.32 [1.02, 1.71], p = 0.034) (Fig. 2).

Conclusion: Pesticide exposure was linked to earlier AAO in PD, increased risk of dyskinesia, a tremor-dominant phenotype, RBD, hyposmia/anosmia, pain, and restless legs syndrome. These findings highlight the potential role of pesticide exposure in PD clinical outcomes, warranting further investigation into the mechanisms behind these associations.

Table 1

Table 2

Figure 1

Figure 2

References: References:
1. Cressatti M, Pinilla-Monsalve GD, Blais M, Normandeau CP, Degroot C, Kathol I, et al. Advancing Parkinson’s disease research in Canada: The Canadian Open Parkinson Network (C-OPN) cohort. J Parkinsons Dis. 2024;14(7):1481–94.
2. Gunnarsson LG, Bodin L. Occupational exposures and neurodegenerative diseases-A systematic literature review and meta-analyses. Int J Environ Res Public Health. 2019 Jan 26;16(3):337.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/association-between-pesticide-exposure-and-clinical-outcomes-in-parkinsons-disease-a-propensity-matched-cohort-study/