Muscle Strength: A Better Index of Mortality and Low Physical Performance than Muscle Mass in Elderly

Abstract

Introduction: Sarcopenia is defined by a loss of muscle mass and strength. This study was performed to investigate the associations between muscle index (mass and strength) and 5-year mortality or low physical performance.

Methods: We included 396 subjects aged 65 years or older in the analysis. Muscle mass and fat mass were assessed by dual energy X-ray absorptiometry. Leg muscle strength and grip strength were measured using dynamometers. The 5-year mortality and low physical performance (Short Physical Performance Battery score < 9) were clinical outcome measures. Associations between muscle index and clinical outcomes were analyzed. Cox proportional hazard models for mortality and logistic regression models for low physical performance were built.

Results: Leg muscle strength and grip strength were significantly associated with 5-year mortality and low physical performance in men and women. Total muscle mass and appendicular skeletal mass in men and women and appendicular skeletal mass divided by height squared in men were associated with 5-year mortality. No association was found between muscle mass indices and 5-year low physical performance. Leg muscle strength was an independent predictor for low physical performance in men (OR = 0.971

95% CI = 0.945-0.999

P = 0.041) after adjustment for age, fat, cognition and depression. Grip strength was an independent predictor for mortality (HR = 0.959

95% CI = 0.928-0.991

P = 0.014) and low physical performance (OR = 0.950

95% CI = 0.912-0.989

P = 0.012) in men after adjustment for age, fat, cognition and depression.

Conclusions: Muscle strength is a better indicator for 5-year adverse clinical outcomes of mortality and low physical performance than muscle mass. In men, muscle strength is an independent predictor of 5-year adverse clinical outcome.