Adverse Muscle Composition Is an Early Feature of Chronic Kidney Disease and Associates With Poor Function and Comorbidities.

Rational & Objective: Sarcopenia is linked to increased morbidity and mortality in chronic kidney disease (CKD), but its definition and assessment vary considerably across studies. This study evaluated the technical feasibility of magnetic resonance imaging (MRI)-based assessment of adverse muscle composition (AMC)-defined as low muscle volume and high fat infiltration-and its associations with comorbidity, functional performance, and risk for coronary heart disease (CHD) in CKD. Study Design: This is a cross-sectional and prospective study. Settings & Participants: Participants included 11 patients from a single-center hemodialysis (HD) cohort and 903 individuals with CKD from the UK Biobank, along with matched controls without CKD. For each participant, a personalized muscle volume z-score (sex-specific and body size-specific) was calculated and combined with muscle fat infiltration for AMC evaluation. Predictors: Adverse muscle composition. Outcomes: Comorbidity index, functional performance (handgrip strength, walking pace, stair climbing, and falls), and new CHD events. Analytical Approach: In the HD cohort, Spearman rank correlations and Cox proportional-hazards model were used. In the UK Biobank cohort, linear/logistic regression models and Cox proportional-hazards model were used. Results: AMC was present in 45% of the HD cohort and associated with higher comorbidity index. In the UK Biobank, AMC prevalence was greater in CKD versus no CKD (32% vs 25%, P < 0.001). Participants with AMC had worse functional performance (P < 0.001), higher comorbidity index (P < 0.001), and 2-fold increased CHD incidence (P = 0.01). Limitations: Blood samples defining CKD were taken 7-9 years before MRI, and self-reported data on walking pace, falls, stair climbing, and type 2 diabetes. Conclusions: The AMC, assessed by MRI, is a prevalent muscle composition phenotype in CKD and is associated with high prevalence of comorbidity, poor function, and increased risk for CHD.