Integrating a biopsychosocial perspective: WHODAS 2.0 enhances functioning assessment in Parkinson's disease

Functioning is a critical health indicator alongside mortality and morbidity, yet it remains under-assessed in Parkinson's disease (PD), where symptom-based scales predominate. Identifying functional limitations across multiple domains is essential to improve care and guide tailored interventions. The World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0), based on the International Classification of Functioning, Disability and Health (ICF), offers a biopsychosocial measure of disability applicable across conditions and cultures. This cross-sectional study aimed to describe functional impairments across PD severity stages using WHODAS 2.0 and to examine whether stage-related differences remained after adjustment for age, sex, disease duration, education, and socioeconomic status. A total of 352 individuals were grouped by Hoehn & Yahr (H&Y) stages 1 through 4. Remote assessments included the Telephone-Montreal Cognitive Assessment, Beck Depression Inventory, MDS-UPDRS Parts I and II, and WHODAS 2.0. The most affected domains were Mobility, Household Activities, and Participation. Significant differences across H&Y stages were identified in all WHODAS 2.0 domains. Adjusted median regression models showed that H&Y stage remained globally associated with all domains after controlling for age, sex, education, socioeconomic level and disease duration. Self-care, Household Activities, Mobility, and Getting Along showed early differences, whereas Cognition, Participation, Work/School Activities, and overall disability burden became more evident in intermediate and advanced stages. WHODAS 2.0 total scores correlated strongly with MDS-UPDRS Parts I and II, while the WHODAS 2.0 Cognition domain showed a moderate negative correlation with T-MoCA. These findings indicate that WHODAS 2.0 captures stage-related functional profiles across multiple life domains in PD, providing information that complements traditional symptom-based scales. By identifying early limitations in self-care, household activities, mobility, and interpersonal functioning, as well as later involvement of cognition, participation, and work/school activities, WHODAS 2.0 may support person-centered assessment and early multidimensional interventions.