Low lean tissue index is associated with kidney disease progression and mortality in non-dialysis advanced CKD

Body mass index inadequately reflects body composition in advanced chronic kidney disease (CKD). Lean tissue index (LTI), a marker of muscle mass, predicts mortality in CKD, but its association with disease progression is uncertain. We evaluated whether age- and sex-adjusted LTI measured by bioelectrical impedance analysis (BIA) predicts progression to kidney replacement therapy (KRT) and mortality in stage 4 to 5 CKD.

This retrospective cohort study included 145 adults with stage 4 to 5 CKD referred to an advanced CKD outpatient clinic. Body composition was assessed by BIA within 6 mo of referral. Low LTI was defined as values below the 10th percentile using age- and sex-specific reference standards. Associations with outcomes were analyzed using Kaplan-Meier estimates, multivariable Cox regression, and competing-risk analysis.

Mean age was 72 ± 11.8 y, mean estimated glomerular filtration rate was 20.4 ± 4.7 mL/min/1.73 m², and 13.1% had low LTI. During a median follow-up of 28 mo, 49.7% initiated KRT and 37.9% died. Low LTI was associated with poorer renal and overall survival (log-rank P = 0.019 and P = 0.006). In multivariable analysis, low LTI independently predicted progression to KRT (hazard ratio 2.20; 95% confidence interval 1.02-4.75) along with lower estimated glomerular filtration rate and higher albuminuria. After accounting for competing risk of death, the association with KRT was attenuated. Low LTI independently predicted mortality (hazard ratio 4.82; 95% confidence interval 1.84-12.64).

Low lean tissue index is associated with mortality and may identify patients at higher risk of CKD progression. Routine body composition assessment may improve risk stratification in advanced CKD.