Association of Sarcopenia with eGFR and Misclassification of Obesity in Adults with CKD in the United States

Abstract

Background and objectives Muscle wasting is common among patients with ESRD, but little is known about differences in muscle mass in persons with CKD before the initiation of dialysis. If sarcopenia was common, it might affect the use of body mass index for diagnosing obesity in people with CKD. Because obesity may be protective in patients with CKD and ESRD, an accurate understanding of how sarcopenia affects its measurement is crucial.Design, setting, participants, & measurements Differences in body composition across eGFR categories in adult participants of the National Health and Nutrition Examination Survey 1999-2004 who underwent dual-energy x-ray absorptiometry were examined. Obesity defined by dual-energy x-ray absorptiometry versus body mass index and sarcopenia as a contributor to misclassification by body mass index were examined.Results Sarcopenia and sarcopenic obesity were more prevalent among persons with lower eGFR (P trend ,0.01 and P trend ,0.001, respectively). After multivariable adjustment, the association of sarcopenia with eGFR was U-shaped. Stage 4 CKD was independently associated with sarcopenia among participants $60 years old (adjusted odds ratio, 2.58; 95% confidence interval, 1.02 to 6.51 for eGFR=15-29 compared with 60-89 ml/min per 1.73 m 2 ; P for interaction by age=0.02). Underestimation of obesity by body mass index compared with dualenergy x-ray absorptiometry increased with lower eGFR (P trend ,0.001), was greatest among participants with eGFR=15-29 ml/min per 1.73 m 2 (71% obese by dual-energy x-ray absorptiometry versus 41% obese by body mass index), and was highly likely among obese participants with sarcopenia (97.7% misclassified as not obese by body mass index).Conclusions Sarcopenia and sarcopenic obesity are highly prevalent among persons with CKD and contribute to poor classification of obesity by body mass index. Measurements of body composition beyond body mass index should be used whenever possible in the CKD population given this clear limitation.

Pneumonia and hospitalizations in the elderly

“…The potentially nephrotoxic drugs, particularly aminoglycosides, require a regular serum monitoring with frequent assessment of renal function [estimated glomerular filtration rate (eGFR) and creatinine] and this is of great importance especially in frail sarcopenic patients. 38 Since the elderly often have a compromised cardiac function, fluids and electrolytes intravenously should be administered with caution, considering the water balance, the change in body weight and the state of repletion measurable by ultrasound evaluation of the caval diameter. 39 Another event to assess in the elderly is secondary diarrhea in antibiotic-associated colitis, which is common if you are using ampicillin, cephalosporins or clindamycin.…”

Misclassification of Obesity in CKD

“…These figures are intriguingly similar to our report on Swedish patients on dialysis (10): excess fatness was present in up to 65% of our patients, and the majority (.50%) of them was misclassified by BMI cutoffs. The reason for this considerable misclassification in both studies was, by subtraction, reduced muscle mass (sarcopenia), which in the study by Sharma et al (8), increased almost linearly across worsening CKD strata and conveyed the extreme situation that 98% of obese individuals with sarcopenia were not correctly diagnosed by BMI.…”

“…Therefore, differences in the prevalence of sarcopenia in this study might just reflect differences in the age distribution of patients with and without CKD. It is noteworthy that, in the work by Sharma et al (8), the linear increase in patients with sarcopenia across worsening CKD strata flattened out after standardization by age, and although Foley et al (16) reported a higher prevalence of sarcopenia in individuals with CKD stage $3 in the NHANES than in those with normal renal function, simple adjustment for age abrogated this difference. Both aging and the abovementioned body compositional changes lead to frailty.…”

“…Methodological challenges when defining the exposures in the study by Sharma et al (8) limit its applicability in the clinical setting. First, Sharma et al (8) based their findings on a cohort-based cutoff of fatness (.60% of the study population distribution).…”

Considering technique of assessment and method for normalizing skeletal muscle mass

“…Sarcopenic obesity was first defined by Baumgartner, who represents a reduced skeletal muscle mass coupled with an increase in fat mass 5, 6, 7. Sarcopenic obesity specifically was highly prevalent among persons with CKD and not those without CKD 8. Sarcopenic obesity may have a particularly poor prognosis and associated with an increased risk of death in patients with end‐stage renal disease (ESRD) 9.…”