Why Do Older Korean Adults Respond Differently to Activities of Daily Living and Instrumental Activities of Daily Living? A Differential Item Functioning Analysis

Objectives: Culture-based gender norms regarding who performs daily activities can bias the assessment of instrumental activities of daily living (IADL). This study evaluated item-response biases in the activities of daily living (ADL) and IADL among community-living Korean older adults. Methods: The subjects included older Korean participants of the Korean Longitudinal Study of Ageing baseline survey (n=4,164). We performed differential item functioning (DIF) analysis of these data using the Mantel-Haenszel method. Results: We observed different reported levels of disability for eight IADL items among gender, age, and educational level subgroups. After matching for overall functional disability, men were more likely to report limitations in performing various household activities, compared to cognitive activities in women. Conclusions: Cross-national comparisons of ADL and IADL disabilities need to consider item response bias stemming from culture-based gender norms regarding who performs different household activities.