Item response bias was present in instrumental activity of daily living scale in Asian older adults

Abstract

Objective: Item response bias (also called differential item functioning, DIF) in Instrumental Activities of Daily Living (IADL) occurs when members of different groups possessing the same disability level do not have the same probability of responding positively for a given item(s). This study aimed to identify the extent of DIF by gender, age, ethnicity, and dementia groups in IADL estimates in Asian (Chinese, Malays, and Indian) elderly subjects. Methods: Data of 1,072 noninstitutionalized elderly subjects were analyzed using Multiple-Indicator Multiple-Cause (MIMIC) latent variable modeling. Results: Given the same functional level, older elderly were less likely to report needing help with preparing meals; men were more likely to report needing help with preparing meals, doing laundry, and taking medication; Malays and demented elderly were more likely to report needing help with using the telephone. The impact of DIF on group differences in cognitive IADL was highest for ethnicity (58%), followed by gender (50%), and dementia (23%); whereas 92% and 5% of group differences in physical IADL were for gender and age, respectively. Conclusion: Item-response bias in IADL scale by gender, age, ethnicity, and dementia should be considered in direct comparisons of disability status among population groups. © 2007 Elsevier Inc. All rights reserved.