Measuring disability in older adults: The International Classification System of Functioning, Disability and Health (ICF) framework

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Abstract
Background:  Despite the importance of disability to geriatric medicine, no large scale study has validated the activity and participation domains of the International Classification System of Functioning, Disability, and Health (ICF) in older adults. The current project was designed to conduct such as analysis, and then to examine the psychometric properties of a measure that is based on this conceptual structure.Methods:  This was an archival analysis of older adults (n = 1388) who had participated in studies within our Claude D Pepper Older Americans Independence Center. Assessments included demographics and chronic disease status, a 23‐item Pepper Assessment Tool for Disability (PAT‐D) and 6‐min walk performance.Results:  Analysis of the PAT‐D produced a three‐factor structure that was consistent across several datasets: activities of daily living disability, mobility disability and instrumental activities of daily living disability. The first two factors are activities in the ICF framework, whereas the final factor falls into the participation domain. All factors had acceptable internal consistency reliability (>0.70) and test–retest (>0.70) reliability coefficients. Fast walkers self‐reported better function on the PAT‐D scales than slow walkers: effect sizes ranged from moderate to large (0.41–0.95); individuals with cardiovascular disease had poorer scores on all scales than those free of cardiovascular disease. In an 18‐month randomized clinical trial, individuals who received a lifestyle intervention for weight loss had greater improvements in their mobility disability scores than those in a control condition.Conclusion:  The ICF is a useful model for conceptualizing disability in aging research, and the PAT‐D has acceptable psychometric properties as a measure for use in clinical research.