Measurement differences in the assessment of functional limitations for cognitive impairment classification across geographic locations.

INTRODUCTION: The measurement of dementia in cross-national contexts relies on the assessment of functional limitations. We aimed to evaluate the performance of survey items on functional limitations across culturally diverse geographic settings.

METHODS: We used data from the Harmonized Cognitive Assessment Protocol Surveys (HCAP) in five countries (total N = 11,250) to quantify associations between items on functional limitations and cognitive impairment.

RESULTS: Many items performed better in the United States and England compared to South Africa, India, and Mexico. Items on the Community Screening Instrument for Dementia (CSID) had the least variability across countries (SD = 0.73 vs. 0.92 [Blessed] and 0.98 [Jorm IQCODE]), but also the weakest associations with cognitive impairment (median odds ratio [OR] = 2.23 vs. 3.01 [Blessed] and 2.75 [Jorm IQCODE]).

DISCUSSION: Differences in cultural norms for reporting functional limitations likely influences performance of items on functional limitations and may affect the interpretation of results from substantive studies.

HIGHLIGHTS: There was substantial cross-country variation in item performance. Items from the Community Screening Instrument for Dementia (CSID) had less cross-country variability but lower performance. There was more variability in performance of instrumental activities of daily living (IADL) compared to activities of daily living (ADL) items. Variability in cultural expectations of older adults should be taken into account. Results highlight the need for novel approaches to assessing functional limitations.