Background: Physical functioning is an important health domain for adults.
Objective: Evaluate physical functioning items in Medicare beneficiaries.
Research design: Survey data from the 2010 Consumer Assessment of Healthcare Providers and Systems Medicare survey.
Subjects: The 366,701 respondents were 58% female; 38% were 75 or older; 57% had high school education or less.
Measures: Walking, getting in or out of chairs, bathing, dressing, toileting, and eating assessed with 3 response choices: unable to do, have difficulty, do not have difficulty.
Results: Pearson correlations among the 6 items ranged from 0.515 to 0.835 (coefficient α=0.92). A single factor categorical factor analytic model fit the data well (comparative fit index=0.998; root mean square error of approximation=0.083). The item with the highest percentage of respondents reporting no difficulty was eating, followed by toileting, dressing, bathing, getting in and out of a chair, and walking. Threshold parameters from an item response theory-graded response model ranged from -1.983 (between unable to do and have difficulty eating) to -0.551 (between have difficulty and no difficulty walking). Item discrimination parameters ranged from 4.632 (walking) to 8.228 (dressing). IRT-scored physical functioning scores correlated with self-rated general health (r=0.389, n=344,843, P<0.0001) mental health (r=0.296, n=351,254, P<0.0001) and number of chronic conditions (r=-0.229, n=284,507, P<0.0001).
Conclusions: The physical functioning items target relatively easy activities, providing information for a minority of people in the sample with the lowest levels of physical functioning. Items representing higher levels of physical functioning are needed for the majority of the Medicare beneficiaries.