Clinical and psychosocial determinants of functional disability in people with Parkinson’s disease: evidence based on World Health Organization Disability Assessment Schedule (WHODAS 2.0)

Abstract

Background: Parkinson’s disease (PD) is characterized by motor and non-motor symptoms that impair daily activities and social participation. Understanding functional disability in individuals with PD requires a comprehensive approach that considers clinical, functional, and psychosocial factors. Although the progression of PD has been widely studied, gaps remain regarding the relative contribution and interaction of these factors in determining functional disability. Objective: To identify clinical, functional, and sociodemographic predictors of global functional disability in individuals with PD, measured by the total score of the World Health Organization Disability Assessment Schedule (WHODAS 2.0). Methods: This cross-sectional observational study followed STROBE guidelines. Individuals with idiopathic Parkinson’s disease were recruited between September 2024 and August 2025 through community outreach and online contact. Inclusion criteria included neurologist-confirmed diagnosis, dopaminergic treatment, independent ambulation, and access to internet-based assessments. Participants underwent in-person and remote evaluations including WHODAS 2.0, MoCA, BESTest, FES, FSS, MDS-UPDRS I and III, Nine-Hole Peg Test, Hoehn & Yahr staging, and the Brazil Economic Classification Criterion. The primary outcome was global functional disability measured by the total WHODAS 2.0 score, with domain scores analyzed as secondary outcomes. Differences among WHODAS domains were examined using the Friedman test with Bonferroni-corrected Wilcoxon post-hoc comparisons. Predictors of disability were investigated using Multiple Linear Regression models including demographic, clinical, cognitive, and functional variables. An additional model included disease severity (Hoehn & Yahr) to examine its contribution to disability. Statistical significance was set at p < 0.05, and analyses were conducted using Python. Results: Forty eight individuals with Parkinson’s disease were included, predominantly in early to moderate stages (H&Y), presenting a moderate level of functional disability according to WHODAS 2.0. Significant differences were observed across WHODAS domains (χ²(6)=48.6; p<0.001), with greater disability in Activities of Daily Living and Participation, followed by Mobility, while Interpersonal relationships and Work activities showed the lowest impairment. The multiple regression model was significant (R²=0.67; adjusted R²=0.57; p<0.001), although no individual predictor remained statistically significant after adjustment. Including disease severity (H&Y) did not improve the model’s explanatory power. Positive trends were observed between functional disability and fear of falling, fatigue, non-motor symptoms, and to a lesser extent motor symptoms. Conclusion: Functional disability in individuals with PD results from the interaction of multiple clinical and psychosocial factors and is not exclusively explained by disease severity, highlighting the importance of multidimensional assessments in clinical practice.