Association of measured physical performance and demographic and health characteristics with self-reported physical function: implications for the interpretation of self-reported limitations

Grant H Louie,Michael M Ward

doi:10.1186/1477-7525-8-84

Abstract

BackgroundSelf-reported limitations in physical function often have only weak associations with measured performance on physical tests, suggesting that factors other than performance commonly influence self-reports. We tested if personal or health characteristics influenced self-reported limitations in three tasks, controlling for measured performance on these tasks.MethodsWe used cross-sectional data on adults aged ≥ 60 years (N = 5396) from the Third National Health and Nutrition Examination Survey to examine the association between the repeated chair rise test and self-reported difficulty rising from a chair. We then tested if personal characteristics, health indicators, body composition, and performance on unrelated tasks were associated with self-reported limitations in this task. We used the same approach to examine associations between personal and health characteristics and self-reported difficulty walking between rooms, controlling for timed 8-foot walk, and self-reported difficulty getting out of bed, controlling for repeated chair rise test results.ResultsIn multivariate analyses, participants who performed worse on the repeated chair rise test were more likely to report difficulty with chair rise. However, older age, lower education level, lower serum albumin, comorbidities, knee pain, and being underweight were also significantly associated with self-reported limitations with chair rise. Results were similar for difficulty walking between rooms and getting out of bed.ConclusionsSelf-reports of limitations in physical function are influenced by personal and health characteristics that reflect frailty, and should not be interpreted solely as measured difficulty performing the task.

Highlights

Self-reported limitations in physical function often have only weak associations with measured performance on physical tests, suggesting that factors other than performance commonly influence self-reports
Analytic framework To maximize the specificity of the association between physical performance tests and self-reported physical function, we studied performance tests in relation to their corresponding self-reported functions: 1) repeated chair rise test and its relationship with self-reported difficulty rising from a chair; 2) repeated chair rise test and its relationship with self-reported difficulty getting in or out of bed; and 3) 8-foot walk test and its relationship with self-reported difficulty walking between rooms on the same level
Compared to participants included in the study, those who were excluded due to lack of assessment of physical function by physical performance tests had similar demographic characteristics

Summary

Introduction

Self-reported limitations in physical function often have only weak associations with measured performance on physical tests, suggesting that factors other than performance commonly influence self-reports. We tested if personal or health characteristics influenced self-reported limitations in three tasks, controlling for measured performance on these tasks. Self-report is subjective and may be influenced by mood, misjudgment of usual ability, or misinterpretation by the respondent. Despite these potential limitations, self-report questionnaires of physical functioning have face and construct validity [2]. An approach commonly used to test the construct validity of self-reported measures of functioning is to compare responses on these measures with directly-observed or measured performance on similar tasks. Self-reported difficulty in rising from a chair is tested for correlations with measured ability to rise from a chair on a timed test

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