Abstract
BackgroundSingle-item physical activity questions provide a quick approximation of physical activity levels. While recall questionnaires provide a more detailed picture of an individual's level of physical activity, single-item questions may be more appropriate in certain situations. The aim of this study was to evaluate two single-item physical activity questions (one absolute question and one relative question) for test-retest reliability, convergent validity, and discriminant validity, in a sample of older adults.MethodsData was obtained from the Project to Prevent Falls in Veterans, a fall risk-factor screening and modification trial. One question measured absolute physical activity (seldom, moderately, vigorously active) and one measured relative physical activity (more, about as, less active than peers). Test-retest reliability was examined using weighted Kappa statistics (κ) in a sample of 43 subjects. Validity was assessed using correlation coefficients (r) in participants who received clinical assessments (n = 159).ResultsThe absolute physical activity question was more reliable than the relative physical activity question (κ = 0.75 vs. κ = 0.56). Convergent validity, however, was stronger for the relative physical activity question (r = 0.28 to 0.57 vs. r = 0.10 to 0.33). Discriminant validity was similar for both questions. For the relative physical activity question, there was moderate agreement when this question was re-administered seven days later, fair to moderate/good associations when compared with indicators of physical function, and little to no associations when compared with measures hypothesized to be theoretically not related to physical activity.ConclusionsThe relative physical activity question had the best combination of test-retest reliability, convergent validity and discriminant validity. In studies requiring a measure of physical activity, where physical activity is not the primary focus and more detailed measures are not feasible, a single question may be an acceptable alternative.
Highlights
Single-item physical activity questions provide a quick approximation of physical activity levels
The median time between administration of validation measures and physical activity (PA) questions ranged between 33 days for the subset of participants who had been administered both the earlier version of the interRAI Community Health Assessment and Veterans’ Comprehensive Assessment (VCA), and 37 days when considering all participants in the validation sample
There was moderate agreement when this question was re-administered seven days later, fair to moderate or good associations when compared with indicators of physical function, and little to no associations when compared with measures hypothesized to be theoretically not related to PA
Summary
Single-item physical activity questions provide a quick approximation of physical activity levels. While recall questionnaires provide a more detailed picture of an individual’s level of physical activity, single-item questions may be more appropriate in certain situations. For a given research budget, there is typically a trade-off between measurement detail and sample size [1]. Each of these issues is present in the study of physical activity (PA) in older adults. Regular PA assists with maintaining independence and preventing disability These complexities are reflected in the many methods used to measure PA or related energy expenditure in older adults [4,5,6,7]. Examples of direct methods include motion sensors, such as pedometers, accelerometers, and Global Positioning Systems, whereas indirect methods include daily PA records or log books and self-report questionnaires
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