Physical and cognitive domains of the instrumental activities of daily living: Validation in a multiethnic population of Asian older adults

Background. We sought to assess the validity of the physical and cognitive domains of Lawton and Brody's Instrumental Activities of Daily Living (IADL) scale and its cross-cultural applicability across ethnic groups in an Asian population of community-living older adults. Methods. Using data from a random population sample of noninstitutionalized Chinese, Malay, and Indian older adults 60 years old and older in Singapore (N = 1072), we modeled the dimensional structure of the 8-item IADL Scale using exploratory and confirmatory factor analyses, and assessed its convergent and divergent validity using known group differences and strengths of association. Results. Factor analyses yielded two strong and reliable factors representing underlying physical and cognitive dimensions of IADL. The validity of the model was supported by the pattern of associations of the IADL with age, gender, education, self-reported health status, hospitalization, physical comorbidities, dementia and depression, and Mini-Mental State Examination (MMSE) scores. Notably, cognitive IADL showed a greater total effect on MMSE cognitive performance score than did physical IADL, with the effect of physical IADL on MMSE score mostly explained by cognitive IADL. Reasonably good cross-cultural validity was demonstrated among Chinese, Malays, and Indians, with strongest validity for Indians. Conclusion. The eight-item IADL Scale has physical and cognitive domains and is cross-culturally applicable. The cognitive IADL domain taps a set of activities directly related to cognitive functioning.