Heterogeneity in Rate of Decline in Grip, Hip, and Knee Strength and the Risk of All‐Cause Mortality: The Women's Health and Aging Study II

Abstract

To assess the relationship between rate of change in muscle strength and all-cause mortality. Prospective observational study of the causes and course of physical disability. Twelve contiguous ZIP code areas in Baltimore, Maryland. Three hundred seven community-dwelling women aged 70 to 79 at study baseline. The outcome was all-cause mortality (1994-2009); predictors included up to seven repeated measurements of handgrip, knee extension, and hip flexion strength, with a median follow-up time of 10 years. Demographic factors, body mass index, smoking status, number of chronic diseases, depressive symptoms, physical activity, interleukin-6, and albumin were assessed at baseline and included as confounders. The associations between declining muscle strength and mortality were assessed using a joint longitudinal and survival model. Grip and hip strength declined an average of 1.10 and 1.31 kg/year between age 70 and 75 and 0.50 and 0.39 kg/year thereafter, respectively; knee strength declined at a constant rate of 0.57 kg/year. Faster rates of decline in grip and hip strength, but not knee strength, independently predicted mortality after accounting for baseline levels and potential confounders (hazard ratio (HR) = 1.33, 95% confidence interval (95% CI) = 1.06-1.67, HR = 1.14, 95% CI = 0.91-1.41, and 2.62, 95% CI = 1.43-4.78 for every 0.5 standard deviation increase in rate of decline in grip, knee, and hip strength, respectively). Monitoring the rate of decline in grip and hip flexion strength in addition to absolute levels may greatly improve the identification of women most at risk of dying.