Domain-specific severity profiles in a large Turkish Parkinson's disease cohort using MDS-UPDRS cut-offs

Background: Standardized severity thresholds for the MDS-UPDRS facilitate interpretation of symptom burden in Parkinson's disease (PD). However, domain-specific severity profiling using these cut-offs has not been systematically evaluated in Türkiye, and international studies rarely apply them across all MDS-UPDRS domains in real-world cohorts. Objective: To describe domain-specific severity distributions of MDS-UPDRS Parts I–IV in a large multicenter Turkish PD cohort and examine clinical correlates. Methods: In this multicenter cross-sectional study, 1181 patients with PD from five Turkish movement disorder centers were evaluated between January 2023 and July 2025. Severity of each MDS-UPDRS domain was classified as mild, moderate, or severe using validated cut-offs proposed by Martínez–Martín et al. Results: Using the predefined Martínez–Martín cut-offs, 53.0% of patients were classified as mild in Part I and 57.8% in Part II, whereas 50.1% fell within the moderate–severe range in Part III and 73.5% were mild in Part IV. In contrast, MDS-UPDRS Part III showed a shift toward moderate severity, suggesting a relative difference in severity distribution across domains. Disease duration showed the strongest association with domain scores. Conclusion: In this large Turkish PD cohort, patient-reported daily-living and non-motor impairments clustered more frequently within the mild severity range compared with motor examination scores. These findings suggest that sociocultural factors may influence self-reported disease burden and highlight the need for complementary assessment approaches.