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


METHODS
We 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.


RESULTS
In 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.


CONCLUSIONS
Self-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.
Louie
Grant H
GH
Intramural Research Program, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland, USA. grant.louie@nih.gov
Ward
Michael M
MM
D000203:Activities of Daily Living / Q000523:psychology; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001294:Attitude to Health; D001823:Body Composition; D015992:Body Mass Index; D005260:Female; D016330:Frail Elderly; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009749:Nutrition Surveys; D010809:Physical Fitness / Q000502:physiology; D019984:Quality Indicators, Health Care; D013647:Task Performance and Analysis; D014481:United States