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Center for Health Services and Outcomes Research

Innovative Methods – New Tools

Harmonizing Cognitive Assessment in International Surveys on Aging

Cognitive functioning measures are now an integral part of the ongoing Health and Retirement Survey (HRS) and have been incorporated in other international longitudinal studies of aging modeled on the HRS. Measures vary substantially across surveys, however, and have received limited validation.  Item Response Theory (IRT) and Classification and Regression Tree (CART) are new measurement techniques that offer promising approaches to operationalizing equivalent measurement constructs for cognitive functioning and severe cognitive impairment across surveys and countries. Under IRT, comparable scores can be calculated for a measured construct even when different items are administered across groups. CART classifies items with regard to a dependent variable, and in this study was used to develop country- specific algorithms that allowed cross national comparisons of persons most impaired in everyday functioning due to cognitive deficits.

Our aims in this project were to first construct and evaluate standardized scores for global cognitive functioning and severe cognitive impairment, then to use an IRT approach to generate cognitive functioning scores that demonstrate measurement equivalence across surveys, and finally to use a CART approach to develop country-specific combinations of cognitive functioning items that exhibit similar expected impairment in everyday functioning across countries. By using these techniques to “harmonize” the disparate cognitive functioning items used across international studies of aging, this research provides the methodological underpinnings for valid cross-national comparisons of the role of cognitive impairment in health trajectories and the associated challenges to families and societies of providing assistance to older cognitively impaired individuals.

Products:

Chan KS, Gross AL, Pezzin LE, Brandt J, Kasper JD. (in press) Harmonizing measures of cognitive performance across international surveys of aging using Item Response Theory. Journal of Aging and Health.

Chan KS, Kasper JD, Brandt J, Pezzin LE. (2012) Measurement equivalence of Activities of Daily Living (ADL) and Instrumental Activities of Daily Living (IADL) items in nationally and internationally representative surveys of the elderly. Journals of Gerontology Series B: Psychological Sciences and Social Sciences 67(1):121-32. [PMCID: PMC3267026]