Reliability and validity of self-care and mobility accommodations measures in the National Health and Aging Trends Study.

Purpose of the Study: Comprehensive measures of disability accommodations have been lacking in national health and aging studies. This article introduces measures of accommodations developed for the National Health and Aging Trends Study, evaluates their reliability, and explores the validity and reliability of hierarchical classification schemes derived from these measures.
Design and Methods: We examined test-retest reliability for questions about assistive device use, doing activities less often, and getting help from another person with both percentage agreement and kappa (N = 111). Summary measures across activities and several hierarchical classification schemes (e.g., no accommodation, devices/activity reductions only, help) were developed. For the latter, we also evaluated validity by examining correlations with measures of capacity and demographic characteristics (N = 326).
Results: Items about assistive device use and help in the last month were robust (most kappas 0.7-0.9). Activity reduction measures were moderately reliable (around 0.5) but still showed reasonable agreement. Reliabilities for summary measures were good for device use (0.78-0.89) and help (0.62-0.67) but lower, albeit acceptable, for activity reduction (0.53). Hierarchical classifications had acceptable reliability and levels demonstrated hierarchical properties.
Implications: National Health and Aging Trends Study's self-care and mobility accommodation measures offer ample reliability to study adaptation to limitations and can be used to construct a reliable and valid hierarchy.
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