Title: Exploring the Association Between Parkinson’s Disease and Multiple Sclerosis: A Meta-analytic Overview (P9-17.012)
Authors: Yagya Adhikari, Jamir Pitton Rissardo, Sangam Shah, Omar Elmandouh, Ana Leticia Fornari Caprara, and Ian M. Walker
Conference: 2026 AAN, Chicago, IL
Objective
To evaluate the bidirectional relationship between Parkinson’s disease (PD) and multiple sclerosis (MS), including neuromyelitis optica spectrum disorder (NMOSD), using population-based studies and meta-analytic methods.
Background
PD and MS are traditionally considered distinct neurological disorders, but emerging evidence suggests potential overlapping mechanisms. Clarifying their temporal associations may provide insight into shared pathophysiology and inform clinical practice.
Design/Methods
A systematic review of the PubMed database was conducted to identify population-based studies examining the temporal association between PD and MS, including NMOSD. Studies were included if they reported incidence data for MS following PD (PD→MS), PD following MS (MS→PD), or PD following NMOSD. Nine eligible studies were identif
ied. A meta-analysis was performed on five studies with complete comparator data using a random-effects model (DerSimonian-Laird estimator), with risk ratio (RR) as the summary measure. Subgroup analyses were conducted for each direction of association. Publication bias was assessed using Egger’s test, Begg’s test, trim-and-fill method, and fail-safe N calculations (Rosenthal, Orwin, and Rosenberg approaches).
ied. A meta-analysis was performed on five studies with complete comparator data using a random-effects model (DerSimonian-Laird estimator), with risk ratio (RR) as the summary measure. Subgroup analyses were conducted for each direction of association. Publication bias was assessed using Egger’s test, Begg’s test, trim-and-fill method, and fail-safe N calculations (Rosenthal, Orwin, and Rosenberg approaches).
Results
Three studies evaluated PD→MS, five assessed MS→PD, and one examined NMOSD→PD. The overall random-effects RR was 4.88 (95% CI: 1.19–20.00). Subgroup analysis showed a RR of 5.75 (95% CI: 0.44 to 75.02) for PD→MS, 7.50 (95% CI: 3.82 to 14.71) for MS→PD, and 2.22 (95% CI: 0.97 to 5.10) for NMOSD→PD. Heterogeneity was high (I² = 95%), Cochran’s Q was significant (Q = 80.5, p < 0.0001). No publication bias was detected. Rosenthal’s fail-safe N was 51, Orwin’s was 5, and Rosenberg’s was 28, indicating robustness of the findings.
Conclusions
Meta-analytic evidence suggests a potential bidirectional association between PD and MS, with a stronger link observed from MS to PD. Findings appear robust against publication bias but are limited by heterogeneity and missing comparator data.
Citation
Adhikari Y, Rissardo JP, Shah S, Elmandouh O, Caprara AL, Walker IM. Exploring the Association Between Parkinson’s Disease and Multiple Sclerosis: A Meta-analytic Overview (P9-17.012). Neurology 2026;106(11_suppl_1):623. doi: 10.1212/WNL.0000000000213024.
Figure 1. Forest plot shows a bidirectional association between Parkinson’s disease and MS, with stronger risk for MS→PD and substantial heterogeneity across studies.