• kidney function;
  • elderly;
  • weight loss;
  • body composition;
  • sarcopenia

OBJECTIVES: To assess the association between kidney function and change in body composition in older individuals.

DESIGN: Prospective cohort study.

SETTING: Two sites, Pittsburgh, Pennsylvania, and Memphis, Tennessee.

PARTICIPANTS: Three thousand twenty-six well-functioning, participants aged 70 to 79 in the Health, Aging and Body Composition Study.

MEASUREMENTS: Body composition (bone-free lean mass and fat mass) was measured using dual x-ray absorptiometry annually for 4 years. Kidney function was measured at baseline according to serum creatinine (SCr). Comorbidity and inflammatory markers were evaluated as covariates in mixed-model, repeated-measures analysis.

RESULTS: High SCr was associated with loss of lean mass in men but not women, with a stronger relationship in black men (P=.02 for difference between slopes for white and black men). In white men, after adjustment for age and comorbidity, higher SCr remained associated with loss of lean mass (−0.07±0.03 kg/y greater loss per 0.4 mg/dL (1 standard deviation (SD)), P=.009) but was attenuated after adjustment for inflammatory factors (−0.05±0.03 kg/y greater loss per SD, P=.10). In black men, the relationship between SCr and loss of lean mass (−0.19±0.04 kg/y per SD, P<.001) persisted after adjustment for inflammation and overall weight change.

CONCLUSION: Impaired kidney function may contribute to loss of lean mass in older men. Inflammation appeared to mediate the relationship in white but not black men. Future studies should strive to elucidate mechanisms linking kidney disease and muscle loss and identify treatments to minimize loss of lean mass and its functional consequences.