Correlates of performance-based measures of muscle function in the elderly: The cardiovascular health study

Background. It is unknown how much age-related changes in muscle performance represent normal aging versus the effects of chronic disease and life style. We examined the correlates of four performance measures - gait speed, timed chair stands (TCS), grip strength, and maximal inspiratory pressure (MIP) - using baseline data from the Cardiovascular Health Study (CHS), a population-based study of risk factors for heart disease and stroke in persons ≤age 65. Methods. We analyzed data from the 5,201 CHS participants. Variables were arranged into nine categories: Personal Characteristics, Anthropometry, Physical Condition, Reported Functional Status, Subjective Health, Psychological Factors, Symptoms, Cognitive Status, Habits and Lifestyle, and Prevalent Disease. Independent correlates were identified using stepwise linear regression. Results. The regression models explained 17.7-25.4% of the observed variability. Although age significantly correlated with each measure, it explained little of the variability (≤ 5.7%). Anthropometric features plus physical condition explained 14.0-17.4% of the variability for grip strength and MIP, but 2.8-12.9% of the variability for gait speed and the log of TCS. Subjective health anti psychological factors explained 1.8-9.4% of the variability in gait speed and the log of TCS, but ≤ 1.2% of the variability in grip strength and MIP. Variables for prevalent disease explained ≤ 1.3% of the variability in each measure. Conclusions. After age 64, age explained little of the variability in muscle performance in a large sample of mostly functionally intact, community-dwelling older persons. Complex measures such as gait speed were more associated with subjective factors than were direct measures of strength. Prevalent disease contributed surprisingly little to muscle performance.