Comparative Associations of Muscle Mass and Muscle Strength with Mortality in Dialysis Patients

TLDR

Reduced muscle mass and strength are common in dialysis patients, yet muscle strength can decline even when muscle mass is preserved. The study investigates the phenotype and mortality associations of isolated or combined loss of muscle mass and strength (sarcopenia) in dialysis patients. A prospective cohort of 330 incident dialysis patients (mean age 53 ± 13 years, 203 men) was followed for up to five years. Low muscle strength, but not low muscle mass alone, was independently associated with higher mortality risk, and strength deficits were more strongly linked to aging, protein‑energy wasting, inactivity, inflammation, and death.

Abstract

Reduced muscle mass and strength are prevalent conditions in dialysis patients. However, muscle strength and muscle mass are not congruent; muscle strength can diminish even though muscle mass is maintained or increased. This study addresses phenotype and mortality associations of these muscle dysfunction entities alone or in combination (i.e., concurrent loss of muscle mass and strength/mobility, here defined as sarcopenia).This study included 330 incident dialysis patients (203 men, mean age 53±13 years, and mean GFR 7±2 ml/min per 1.73 m(2)) recruited between 1994 and 2010 and followed prospectively for up to 5 years. Low muscle mass (by dual-energy x-ray absorptiometry appendicular mass index) and low muscle strength (by handgrip) were defined against young reference populations according to the European Working Group on Sarcopenia in Older People.Whereas 20% of patients had sarcopenia, low muscle mass and low muscle strength alone were observed in a further 24% and 15% of patients, respectively. Old age, comorbidities, protein-energy wasting, physical inactivity, low albumin, and inflammation associated with low muscle strength, but not with low muscle mass (multivariate ANOVA interactions). During follow-up, 95 patients (29%) died and both conditions associated with mortality as separate entities. When combined, individuals with low muscle mass alone were not at increased risk of mortality (adjusted hazard ratio [HR], 1.23; 95% confidence interval [95% CI], 0.56 to 2.67). Individuals with low muscle strength were at increased risk, irrespective of their muscle stores being appropriate (HR, 1.98; 95% CI, 1.01 to 3.87) or low (HR, 1.93; 95% CI, 1.01 to 3.71).Low muscle strength was more strongly associated with aging, protein-energy wasting, physical inactivity, inflammation, and mortality than low muscle mass. Assessment of muscle functionality may provide additional diagnostic and prognostic information to muscle-mass evaluation.