Change in motor function and risk of mortality in older persons

OBJECTIVES: To assess the association between change in motor function and mortality. DESIGN: Prospective, observational cohort study. SETTING: Approximately 40 retirement communities across the Chicago metropolitan area participating in the Rush Memory and Aging Project. PARTICIPANTS: Eight hundred thirty-seven community-based older persons without dementia. MEASUREMENTS: Change in composite measures of motor performance and muscle strength. RESULTS: During a mean follow-up of 2.2 years, 81 persons died. In a proportional hazards model adjusted for age, sex, education, and body mass index, each 1-unit increase in the level of baseline motor performance was associated with an approximately 10% decrease in risk of mortality (hazard ratio (HR)=0.901, 95% confidence interval (CI)=0.863-0.941), and each unit of annual increase in motor performance was associated with an approximately 11% decrease in the risk of mortality (HR=0.887, 95% CI=0.835-0.942). In a similar model, each 1-unit increase in the level of baseline strength was associated with an approximately 9% decrease in the risk of mortality (HR=0.906, 95% CI=0.859-0.957), and each 1-unit annual increase in strength was associated with an approximately 10% decrease in the risk of mortality (HR=0.898, 95% CI=0.809-0.996). These results were similar when men and women were analyzed separately and after controlling for physical activity, cognition, and chronic disorders. When motor performance and muscle strength were examined in a single model, only baseline and annual change in motor performance were associated with mortality. CONCLUSION: Level and rate of change in strength and motor performance are associated with mortality. The attenuation of the association between strength and mortality by motor performance suggests that motor function is not a unitary process and that its components may vary in their associations with adverse health consequences in older persons.