Abstract: FR-PO504

Conventional Measures of Body Composition Underestimate Sarcopenia and Overestimate Obesity in CKD

Session Information

Category: Chronic Kidney Disease (Non-Dialysis)

  • 304 CKD: Epidemiology, Outcomes - Non-Cardiovascular

Authors

  • Ziolkowski, Susan, Stanford University , Stanford , California, United States
  • Long, Jin, Stanford University , Palo Alto, California, United States
  • Chertow, Glenn Matthew, Stanford University School of Medicine, Palo Alto, California, United States
  • Leonard, Mary B., Stanford School of Medicine, Stanford, California, United States
Background

Fat and lean mass are directly correlated. Therefore, conventional definitions of sarcopenia (S) based on lean mass fail to capture low lean relative to fat, i.e. relative sarcopenia (RS) in those with greater adiposity. Recent data suggest RS better predicts incident morbidity than does S. Percent body fat (%BF) overestimates the prevalence of obesity if lean mass is low, while body mass index (BMI, kg/m2) can underestimate. Fat mass indexed to height (kg/m2) helps to address this limitation.

Methods

DXA appendicular lean mass index (ALMI, kg/m2) and FMI were assessed in 13,980 NHANES participants. ALMI, FMI, and ALMI relative to FMI were expressed as sex- and race/ethnicity-specific standard deviation scores compared with young adults (T-scores) and for age. S was defined as ALMI T-score < -2, and RS as ALMI relative to FMI T-score < -2. Excess adiposity was defined using sex- and race/ethnicity specific FMI cutpoints and conventional BMI and %BF cutpoints. GFR was estimated using creatinine (eGFRcr) and cystatin C (eGFRcys).

Results

The prevalence of RS was higher than the prevalence of S, especially in CKD stages 3b (17 vs 6%) and 4 (36 vs 6%) using eGFRcr; these stages were associated with the highest FMI, accounting for the higher prevalence of RS vs S. In multivariable logistic regression, CKD stage was independently associated with lower ALMI relative to FMI for age, adjusted for smoking, physical activity and cardiovascular disease (OR stage 3b=1.47, stage 4=1.99, stage 5=2.38, vs eGFRcys > 90; p trend=0.05). The prevalence of obesity increased with CKD stage through stage 4, and was lower in stage 5 using FMI, BMI and %BF definitions. BMI and %BF under- and overestimated obesity prevalence, e.g., in CKD Stage 4, the prevalence of obesity was: BMI 42%, FMI 55%, %BF = 72%. CKD was not associated with obesity by FMI, adjusted for race, age, diabetes, liver disease, physical activity and cardiovascular disease.

Conclusion

In CKD, S underestimates muscle deficits and %BF overestimates the prevalence of obesity. CKD is independently associated with low lean mass relative to fat mass (RS) but is not associated with excess adiposity. Future studies are needed to determine how RS and excess adiposity (as defined by FMI) relate to morbidity and mortality in CKD.

Funding

  • NIDDK Support