Unlike the general population, a higher body mass index (BMI) is associated with greater survival among patients with chronic kidney disease (CKD). This "obesity paradox" may be due to limitations of BMI as a measure of adiposity in CKD. Both BMI and body fat percentage (BF%) are used to classify obesity, but outcomes may vary. Therefore, we investigated the 2 different cutoffs for diagnosing obesity (BMI ≥28 kg/m² or BF% >25% for men and >35% for women) and the impact on all-cause mortality in CKD. A total of 326 patients with non-dialysis-dependent CKD were prospectively followed for a median of 4.9 years (range 2.9-5.3). BF% and lean body mass were determined using the Body Composition Monitor, a novel multifrequency bioimpedance spectroscopy device. Covariates included age, gender, diabetes, cardiovascular disease, estimated glomerular filtration rate, proteinuria, and high-sensitivity C-reactive protein. Per the BMI definition, 27.9% of patients were obese. However, 48.8% of patients were obese according to the BF% definition. A BMI ≥28 kg/m² had a moderately high specificity of 83.2% but a low sensitivity of 39.6% for detecting BF%-defined obesity. In the fully adjusted models containing both BMI and BF%, obesity defined by BMI was associated with a significantly lower risk of death (hazard ratio [HR]: 0.23; 95% CI: 0.07-0.71; P = 0.011), whereas the result was reversed when obesity was defined by BF% (HR: 2.75; 95% CI: 1.28-5.89; P = 0.009). When patients were classified into 4 distinct groups based on both the BMI and BF% cutoffs for obesity, a considerable proportion of patients (29.4%) had excess body fat in the context of a normal BMI. These patients were more likely to have lower lean body mass (i.e., sarcopenic obesity) and had higher mortality compared with patients with obesity defined by both BMI and BF% (HR: 5.11; 95% CI: 1.43-18.26; P = 0.012). Diagnostic discordance between BMI and BF% may partly explain the obesity paradox. Proper diagnosis of obesity in patients with CKD is required for both risk prediction and treatment.

Little is known about the relationship between gut dysbiosis, inflammation, and adverse outcomes in patients with chronic kidney disease. We examined the association of microbial diversity with all-cause mortality in hemodialysis patients. The gut microbiota was assessed by 16S ribosomal RNA gene sequencing. During a median follow-up of 2.1 years, the adjusted risk of death among patients with higher diversity (above median) was 74% lower than that among patients with lower diversity (below median). We then compared the microbial composition between nonsurvivors and survivors in a matched case-control study. We observed significantly lower microbial diversity and higher proinflammatory cytokines among nonsurvivors than survivors. Specifically, the relative abundance of Succinivibrio and Anaerostipes, two short-chain fatty acid-producing bacteria, was markedly reduced in nonsurvivors. Thus, a unique gut microbial composition is associated with an increased risk of mortality among hemodialysis patients and may be used to identify subjects with a poor prognosis.

Malnutrition is prevalent in patients with chronic kidney disease (CKD). However, current nutrition screening tools are not specific to the CKD population. In the present study, we aimed to investigate whether the geriatric nutritional risk index (GNRI), a simple tool designed for assessing nutrition-related risks in the elderly population, is associated with unique aspects of CKD such as fluid status, residual renal function, proteinuria, and inflammation, and whether it predicts clinical outcomes. The GNRI was calculated by incorporating serum albumin and anthropometric measurements in 326 patients with nondialysis stage 3–5 CKD who were followed up from September 2011 to March 2017 for end-stage renal disease (ESRD) and the composite outcome of all-cause death and cardiovascular events. Patients were stratified into tertiles according to baseline GNRI levels. Patients in the lowest GNRI tertile were more likely to have significantly higher levels of overhydration, proteinuria, and serum inflammatory markers and tended to have lower lean body mass and estimated glomerular filtration rate when compared with patients in the middle and upper GNRI tertiles. In multivariate linear regression analyses, the GNRI was independently associated with overhydration, proteinuria, and interleukin-6. During a median follow-up of 4.9 years, 101 patients developed ESRD; 40 deaths, and 68 cardiovascular events occurred. Patients in the lowest GNRI tertile had significantly increased risks of ESRD (hazard ratio (HR): 3.15, 95% confidence interval (CI): 1.95–5.07, p < 0.001) and the composite outcome (HR: 1.79, 95% CI: 1.10–2.92, p = 0.019) in fully adjusted models (reference: middle and upper GNRI tertiles). The GNRI takes CKD-specific health conditions into account. In addition, CKD patients with lower GNRI scores had a significantly higher risk of adverse clinical outcomes. Our findings suggest that the GNRI is an appropriate tool for nutrition screening and a prognostic predictor among patients with nondialysis stage 3–5 CKD.

Sarcopenia is frequently encountered in patients undergoing peritoneal dialysis (PD). We evaluated and compared the diagnostic performance of a strength, assistance walking, rise from a chair, climb stairs, and falls (SARC-F) questionnaire, SARC-F combined with calf circumference (SARC-CalF), and calf circumference (CC) for screening sarcopenia among patients undergoing PD. We measured the appendicular skeletal muscle mass, evaluated using a multifrequency bioimpedance spectroscopy device, handgrip strength, and 6-m gait speed. SARC-F, SARC-CalF, and CC were obtained in all participants. Sarcopenia was defined using four different diagnostic criteria, including the Asian Working Group for Sarcopenia (AWGS) 2019, revised European Working Group on Sarcopenia in Older People (EWGSOP2), Foundation for the National Institutes of Health (FNIH), and International Working Group on Sarcopenia (IWGS). Among 186 enrolled patients undergoing PD (mean age 57.5 ± 14.1 years), the sarcopenia prevalence was 25.8–38.2% using the four definitions. The discriminative powers of SARC-CalF (range 0.648–0.748) and CC (range 0.652–0.813) against the four definitions were better than those exhibited by SARC-F (range 0.587–0.625), which achieved significant difference, except when adopting the criteria of the FNIH. After stratification by gender, the superiority of SARC-CalF and CC over SARC-F was maintained when AWGS 2019, EWGSOP2, and IWGS were applied. In conclusion, CC and SARC-CalF outperformed SARC-F in the diagnostic accuracy of sarcopenia among patients undergoing PD.