Benchmarking functional status in older adults

Objective: To characterize the manner of functional status difficulties with age across multiple functional domains: lower extremity function, upper extremity function, and cognitive/social function. Construct validity of a functional status measure composed of these domains was assessed as part of this goal.

Design: Cross-sectional survey of the community-dwelling civilian population in the United States.

Setting: Community.

Participants: Community-dwelling adults aged 60 years and older (N=7968).

Interventions: Not applicable.

Main outcome measures: Model fit of a 20-item functional status measure to a confirmatory factor analysis model was assessed with the root mean square error of approximation and the root mean square residual. Functional status benchmarks for age were developed with curves plotting activity difficulty percentiles versus age for the general U.S. population.

Results: The 20-item activity difficulty index modeled as a 3-factor construct had a root mean square error of approximation of .045 and a root mean squared residual of .052, indicating good fit. Benchmarks based on percentiles show that the median activity difficulty score is quite low for the full range studied but that there is a steady increase with increasing age. The domain regarding cognition and social function appeared to be less sensitive than the upper and lower extremity skills domains to increasing age.

Conclusions: A broad measure of difficulty with functional activities can be meaningfully treated as a 3-domain construct. The scores represented by the index measuring this construct can be used to compare patients to a national sample of age-matched individuals to assess functional status using normative values.