Diagnostic accuracy of Instrumental Activities of Daily Living for dementia in community-dwelling older adults

Abstract

Background: many people living with dementia remain underdiagnosed and unrecognised. Screening strategies are important for early detection.

Objective: to examine whether the Lawton's Instrumental Activities of Daily Living (IADL) scale, compared with other cognitive screening tools-the Mini-Mental State Examination (MMSE), and the Ascertain Dementia 8-item Informant Questionnaire (AD8)-can identify older (≥ 65 years) adults with dementia.

Design: population-based cross-sectional observational study.

Setting: all 19 counties in Taiwan.

Participants: community-dwelling older adults (n = 10,340; mean age 74.87 ± 6.03).

Methods: all participants underwent a structured in-person interview. Dementia was identified using National Institute on Aging-Alzheimer's Association core clinical criteria for all-cause dementia. Receiver operator characteristic curves were used to determine the discriminant abilities of the IADL scale, MMSE and AD8 to differentiate participants with and without dementia.

Results: we identified 917 (8.9%) participants with dementia, and 9,423 (91.1%) participants without. The discriminant abilities of the MMSE, AD8 and IADL scale (cutoff score: 6/7; area under curve = 0.925; sensitivity = 89%; specificity = 81%; positive likelihood ratio = 4.75; accuracy = 0.82) were comparable. Combining IADL with AD8 scores significantly improved overall accuracy: specificity = 93%; positive likelihood ratio = 11.74; accuracy = 0.92.

Conclusions: our findings support using IADL scale to screen older community-dwelling residents for dementia: it has discriminant power comparable to that of the AD8 and MMSE. Combining the IADL and the AD8 improves specificity.

Keywords: Alzheimer’s disease; dementia; diagnostic accuracy; instrumental activity of daily living; older people; screen.