The relationship between physical performance measures and independence in instrumental activities of daily living

OBJECTIVES: Understanding the relationship between physical capacity and functional status is required to design exercise interventions to maintain independent living. This study assessed the importance of physical performance in maintaining independence in Instrumental Activities of Daily Living (IADL). DESIGN: A pre-planned meta-analysis of cross-sectional data from six sites of the Frailty and Injury: Cooperative Studies of Intervention Trials (FICSIT). Linear regression was used to estimate the relationship between physical performance and IADL. PARTICIPANTS: 2190 community dwelling older subjects. MEASUREMENTS: IADL was the dependent variable; gait velocity, balance function, grip strength and chair rise time were the predictor variables. Age, gender, education, falls self-efficacy, and cognitive status were covariates. RESULTS: Gait velocity, balance function, and grip strength were independently related to IADL deficits, after correcting for covariates. The linear slopes were relatively steep. For gait, a decrease of 0.1 m s^-1 was associated with 0.10 (95% CI: 0.17, 0.04) increase in IADL deficits, which is equivalent to 1 ADL deficit in 10 subjects. The linear slopes for hand grip and balance were similar or steeper. In the sites where chair stand time was measured, an increase of 1 second in the time to rise was associated with a 0.14 (0.04, 0.24) increase in IADL deficits. The relationships found in the meta-analytic analysis were consistent across sites which enrolled subjects with widely varying levels of physical performance. CONCLUSION: Simple measures of physical performance were strongly associated with IADL independence after correcting for many previously identified predictors of functional status. The data from this meta-analysis support testing interventions designed to improve physical performance to determine whether improved performance can maintain or improve independence in IADLs.