Disability Measurement for Korean Community-Dwelling Adults With Stroke: Item-Level Psychometric Analysis of the Korean Longitudinal Study of Ageing

Abstract

Objective: To investigate the psychometric properties of the activities of daily living (ADL) instrument used in the analysis ofKorean Longitudinal Study of Ageing (KLoSA) dataset.Methods: A retrospective study was carried out involving 2006 KLoSA records of community-dwelling adults diagnosed withstroke. The ADL instrument used for the analysis of KLoSA included 17 items, which were analyzed using Rasch modelingto develop a robust outcome measure. The unidimensionality of the ADL instrument was examined based on confirmatoryfactor analysis with a one-factor model. Item-level psychometric analysis of the ADL instrument included fit statistics, internalconsistency, precision, and the item difficulty hierarchy.Results: The study sample included a total of 201 community-dwelling adults (1.5% of the Korean population with an age over 45years; mean age=70.0 years, SD=9.7) having a history of stroke. The ADL instrument demonstrated unidimensional construct. Twomisfit items, money management (mean square [MnSq]=1.56, standardized Z-statistics [ZSTD]=2.3) and phone use (MnSq=1.78,ZSTD=2.3) were removed from the analysis. The remaining 15 items demonstrated good item fit, high internal consistency (personreliability=0.91), and good precision (person strata=3.48). The instrument precisely estimated person measures within a widerange of theta (-4.75 logits < q < 3.97 logits) and a reliability of 0.9, with a conceptual hierarchy of item difficulty.Conclusion: The findings indicate that the 15 ADL items met Rasch expectations of unidimensionality and demonstrated goodpsychometric properties. It is proposed that the validated ADL instrument can be used as a primary outcome measure forassessing longitudinal disability trajectories in the Korean adult population and can be employed for comparative analysis ofinternational disability across national aging studies