Are IADLs comparable across countries? Sociodemographic associates of harmonized IADL measures

Background and aims: Independence in Instrumental Activities of Daily Living (IADLs) is determined not only by physical ability but also by the environmental and cultural surroundings of the individual. The present study describes the harmonization of data on IADL functioning of the Comparison of Longitudinal European Studies on Aging (CLESA) Project. The focus of this report is to examine the comparability of IADLs across countries and to study the association of IADLs with age, gender and socioeconomic status, and the scalability of the measure. Methods: The study base includes data from five European countries (Finland, Italy, the Netherlands, Spain, Sweden) and Israel, for older people aged 65-89 living both in the community and in institutions, for a total of 11557 subjects. In this report, only community-dwelling respondents were included (N=8420). The common IADL items in all six countries were: preparing meals, shopping, and doing housework. The analyses include how these items are distributed by age group and gender, and the associations between independence in these items and socioeconomic status (SES) with logistic regression modeling. The scale properties of these three items are also examined. Results: Independence in IADLs decreases steadily with age in all countries. Associations with gender and SES follow largely similar patterns across countries. The reliability of the 3-item scale is satisfactory in most countries, and Cronbach's α-coefficient for the complete CLESA sample was 0.75. Conclusions: The associations between sociodemographic variables and independence in preparing meals, shopping, and doing housework are similar across countries. Results suggest that the predictors of IADLs in different countries are comparable.