Beyond Symptoms: WHODAS as a Biopsychosocial Measure to Complement Functioning Assessment in Parkinsons Disease

Functionality is considered the third health indicator, complementing the traditional mortality and morbidity metrics. However, functionality is rarely assessed systematically in Parkinsons disease (PD) clinical practice and research, where symptom-based scales predominate. Identifying declines across various dimensions of functionality in PD is essential for patient education, disease management, and guiding new intervention strategies. The World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0) is a comprehensive assessment tool developed by the World Health Organization (WHO) based on the International Classification of Functioning, Disability and Health (ICF) to standardize the measurement of functionality and disability impacts across diverse health conditions and cultural contexts. This study aimed to characterize functionality across PD severity stages using the WHODAS 2.0, independent of age, sex, socioeconomic status (SEC), and education. A total of 352 patients were divided into four clinically severity PD stage groups according to the Hoehn & Yahr (H&Y) scale. The age, sex, SEC and education levels were controlled to guarantee paired groups. All participants were evaluated remotely using the Telephone - Montreal Cognitive Assessment (T-MoCA), Beck Depression Inventory (BDI), Movement Disorder Society - Unified Parkinsons Disease Rating Scale, Part I (MDS-UPDRS I) and Part II (MDS-UPDRS II) and WHODAS 2.0. The most affected functionality dimensions were Mobility, Activities of Daily Life related to the Household, and Participation. The nonparametric Kruskal-Wallis test revealed a significant effect of the group for all functionality dimensions. Notably, Mobility, Activities of Daily Life related to the Household, and Self-Care showed a gradual decline starting from stage 1 of H&Y. In contrast, Cognition, Getting Along and Participation exhibited progressive impairment only from stage 2 of H&Y. This study is the first to describe functionality in PD using WHODAS 2.0 across severity stages controlling for key demographic factors. Findings highlight that WHODAS captures functional limitations not identified by symptom-focused scales such as MDS-UPDRS. Incorporating WHODAS into routine assessment may improve patient-centered care by informing interventions targeting functional limitations from early disease stages. HighlightsWHODAS 2.0 captures functionality domains not assessed by MDS-UPDRS. Functional decline in mobility, self-care, and household tasks starts at early PD stages. Participation, cognition, and interpersonal relationships decline from stage 2 onwards. Functionality decline is independent of age, sex, education, and socioeconomic status. WHODAS provides a biopsychosocial assessment essential for person-centered PD care.