Body composition is associated with clinical outcomes in patients with non-dialysis-dependent chronic kidney disease

Preventive Nephrology: The Role of Obesity in Different Stages of Chronic Kidney Disease

BACKGROUND

Obesity is increasing worldwide and has become a nontraditional risk factor in chronic kidney disease (CKD).

SUMMARY

Obesity-related nephropathy may aggravate renal complications of the metabolic syndrome and progress to advanced CKD stages, while obesity in early stages of CKD is clearly related to the development of kidney disease. A high body mass index (BMI) in advanced CKD stages and dialysis is an advantage for survival (so called "obesity paradox"). A high lean body to fat mass index indicates a beneficial state of body composition. In contrast, loss of muscle mass with increasing fat mass causes "sarcopenia obesity," which is related to unfavorable outcomes in renal replacement therapy. Obesity (BMI > 30-35) in renal transplant recipients is associated with a higher risk of complications such as delayed graft function, increased rates of rejection, and graft loss. While conservative management of morbid obesity is failing in most cases, bariatric surgery seems to be an option in some cases to improve renal complications in the early stage of CKD or in transplant candidates.

KEY MESSAGE

In conclusion, obesity is increasingly prevalent among CKD patients. Adequate management with respect to the specific role of obesity in different stages of CKD should be integrated in routine renal care.

Factors associated with survival in dogs with chronic kidney disease

Background: Chronic kidney disease (CKD) is associated with morbidity and mortality in dogs. Plasma fibroblast growth factor‐23 (FGF‐23) concentration is an independent predictor of CKD progression and survival in cats and people with CKD.

Objectives: To investigate the relationship among FGF‐23, parathyroid hormone (PTH), vitamin D metabolites, and other clinical variables with survival time in dogs with CKD.

Animals: Twenty‐seven azotemic CKD dogs.

Methods: Dogs were recruited prospectively into the study and followed until death or study conclusion. Dogs were International Renal Interest Society (IRIS) staged into stage 2 (n = 9), stage 3 (n = 12), and stage 4 (n = 6) CKD. Survival times were calculated from the date of study inclusion. Univariable Cox regression was used to assess variables associated with survival including body condition score (BCS), muscle condition score, hematocrit, creatinine, CKD stage, serum phosphorus, urine protein:creatinine ratio (UPC), calcium phosphorus product (CaPP), PTH, 25‐hydroxyvitamin D, 1,25‐‐dihydroxyvitamin D, and FGF‐23 concentrations.

Results: Significant hazard ratios (hazard ratio; 95% confidence interval; P value) were as follows: BCS < 4/9 (1.579; 1.003‐2.282; P = .05), muscle atrophy (2.334; 1.352‐4.030; P = .01), increased creatinine (1.383; 1.16‐1.64; .01), hyperphosphatemia (3.20; 1.357‐7.548; P = .005), increased UPC (3.191; 1.310‐7.773; P = .01), increased CaPP (4.092; 1.771‐9.454; P = .003), and increased FGF‐23 (2.609; 1.090‐6.240; P = .05). Survival times for each IRIS CKD stage were significantly different (P = .01).

Conclusions and Clinical Importance: Multiple variables, including FGF‐23, were associated with duration of survival in CKD dogs. FGF‐23 could be a prognostic marker in dogs with CKD.

Association between Geriatric Nutrition Risk Index and low muscle mass in Chinese elderly people

BACKGROUND/OBJECTIVES

The aim of the study was to evaluate the relationship between Geriatric Nutrition Risk Index (GNRI) and low muscle mass (LMM) in elderly people.

SUBJECTS/METHODS

A cross-sectional study was carried out in Chinese PLA General Hospital with 3240 participants who underwent a health check-up examination between February 2016 and February 2017. Linear regression and logistic regression were used to examine the relationship between GNRI and LMM.

RESULTS

The mean age of the participants in the study was 64.6 years. The mean appendicular skeletal muscle mass index (ASMI) was 8.92 ± 0.93 kg/m² in men and 7.62 ± 0.73 kg/m² in women. The incidences of LMM were 7.9% in men and 3.7% in women. Linear regression demonstrated that GNRIs were positively correlated with ASMIs in both men and women (β = 0.055 for men and 0.039 for women, all P < 0.001). The cut-off point of the GNRI in elderly people for LMM was 104.0 in men and 107.0 in women and were identified by Classification and Regression Trees (CART). Logistic regression showed that both men and women with decreased GNRIs had higher ratios of LMM [odds ratio (OR) = 3.904 for men and 4.486 for women, P < 0.001 and P = 0.001, respectively].

CONCLUSIONS

Elderly people with a low GNRI had a higher incidence of LMM, which suggested that GNRI had a close relationship with LMM and that it could be a good indicator in identifying senior people who need further nutritional support and physical activity.

Impact of Misclassification of Obesity by Body Mass Index on Mortality in Patients With CKD

Introduction

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.

Methods

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.

Results

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).

Conclusion

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.