Racial and ethnic differences in the association of body mass index and survival in maintenance hemodialysis patients

Physical Activity, Cardiorespiratory Fitness, and the Obesity Paradox with Consideration for Racial and/or Ethnic Differences: A Broad Review and Call to Action

Despite decades of extensive research and clinical insights on the increased risk of all-cause and disease-specific morbidity and mortality due to obesity, the obesity paradox still presents a unique perspective, i.e., having a higher body mass index (BMI) offers a protective effect on adverse health outcomes, particularly in people with known cardiovascular disease (CVD). This protective effect may be due to modifiable factors that influence body weight status and health, including physical activity (PA) and cardiorespiratory fitness (CRF), as well as non-modifiable factors, such as race and/or ethnicity. This article briefly reviews the current knowledge surrounding the obesity paradox, its relationship with PA and CRF, and compelling considerations for race and/or ethnicity concerning the obesity paradox. As such, this review provides recommendations and a call to action for future precision medicine to consider modifiable and non-modifiable factors when preventing and/or treating obesity.

Patient Survival With Extended Home Hemodialysis Compared to In-Center Conventional Hemodialysis

Introduction

More frequent and/or longer hemodialysis (HD) has been associated with improvements in numerous clinical outcomes in patients on dialysis. Home HD (HHD), which allows more frequent and/or longer dialysis with lower cost and flexibility in treatment planning, is not widely used worldwide. Although, retrospective studies have indicated better survival with HHD, this issue remains controversial. In this multicenter study, we compared thrice-weekly extended HHD with in-center conventional HD (ICHD) in a large patient population with a long-term follow-up.

Methods

We matched 349 patients starting HHD between 2010 and 2014 with 1047 concurrent patients on ICHD by using propensity scores. Patients were followed-up with from their respective baseline until September 30, 2018. The primary outcome was overall survival. Secondary outcomes were technique survival; hospitalization; and changes in clinical, laboratory, and medication parameters.

Results

The mean duration of dialysis session was 418 ± 54 minutes in HHD and 242 ± 10 minutes in patients on ICHD. All-cause mortality rate was 3.76 and 6.27 per 100 patient-years in the HHD and the ICHD groups, respectively. In the intention-to-treat analysis, HHD was associated with a 40% lower risk for all-cause mortality than ICHD (hazard ratio [HR] = 0.60; 95% confidence interval [CI] 0.45 to 0.80; P < 0.001). In HHD, the 5-year technical survival was 86.5%. HHD treatment provided better phosphate and blood pressure (BP) control, improvements in nutrition and inflammation, and reduction in hospitalization days and medication requirement.

Conclusion

These results indicate that extended HHD is associated with higher survival and better outcomes compared to ICHD.

Study on the correlation between bioelectrical impedance analysis index and protein energy consumption in maintenance dialysis patients

BACKGROUND

Protein-energy wasting (PEW) has been reported to be pretty common in maintenance dialysis patients. However, the existing PEW diagnostic standard is limited in clinical use due to the complexity of it. Bioelectrical impedance analysis (BIA), as a non-invasive nutritional assessment method, can objectively and quantitatively analyze the changes of body tissue components under different nutritional states. We aim to explore the association between PEW and BIA and establish a reliable diagnostic model of PEW.

METHODS

We collected cross-sectional data of 609 maintenance dialysis patients at the First Affiliated Hospital, College of Medicine, Zhejiang University. PEW was diagnosed according to International Society of Renal Nutrition and Metabolism (ISRNM) criteria. Among them, 448 consecutive patients were included in the training set for the establishment of a diagnostic nomogram. 161 consecutive patients were included for internal validation. 52 patients from Zhejiang Hospital were included for external validation of the diagnostic model. Correlation analysis of BIA indexes with other nutritional indicators was performed. Logistic regression was used to examine the association of BIA indexes with PEW. 12 diagnostic models of PEW in maintenance dialysis patients were developed and the performance of them in terms of discrimination and calibration was evaluated using C statistics and Hosmer-Lemeshow-type χ2 statistics. After comparing to existing diagnostic models, and performing both internal and external validation, we finally established a simple but reliable PEW diagnostic model which may have great value of clinical application.

RESULTS

A total of 609 individuals from First Affiliated Hospital, College of Medicine, Zhejiang University and 52 individuals from Zhejiang Hospital were included. After full adjustment, age, peritoneal dialysis (compared to hemodialysis), subjective global assessment (SGA, compared to non-SGA) and water ratio were independent risk factors, while triglyceride, urea nitrogen, calcium, ferritin, BCM, VFA and phase angle were independent protective factors of PEW. The model incorporated water ratio, VFA, BCM, phase angle and cholesterol revealed best performance. A nomogram was developed according to the results of model performance. The model achieved high C-indexes of 0.843 in the training set, 0.841 and 0.829 in the internal and external validation sets, respectively, and had a well-fitted calibration curve. The net reclassification improvement (NRI) showed 8%, 13%, 2%, 38%, 36% improvement of diagnostic accuracy of our model compared with "PEW score model", "modified PEW score model", "3-index model", "SGA model" and "BIA decision tree model", respectively.

CONCLUSIONS

BIA can be used as an auxiliary tool to evaluate PEW risk and may have certain clinical application value.

Pathophysiological concepts and screening of cardiovascular disease in dialysis patients

Dialysis patients experience 10-20 times higher cardiovascular mortality than the general population. The high burden of both conventional and nontraditional risk factors attributable to loss of renal function can explain higher rates of cardiovascular disease (CVD) morbidity and death among dialysis patients. As renal function declines, uremic toxins accumulate in the blood and disrupt cell function, causing cardiovascular damage. Hemodialysis patients have many cardiovascular complications, including sudden cardiac death. Peritoneal dialysis puts dialysis patients with end-stage renal disease at increased risk of CVD complications and emergency hospitalization. The current standard of care in this population is based on observational data, which has a high potential for bias due to the paucity of dedicated randomized clinical trials. Furthermore, guidelines lack specific guidelines for these patients, often inferring them from non-dialysis patient trials. A crucial step in the prevention and treatment of CVD would be to gain better knowledge of the influence of these predisposing risk factors. This review highlights the current evidence regarding the influence of advanced chronic disease on the cardiovascular system in patients undergoing renal dialysis.

Low BMI and high waist-to-hip ratio are associated with mortality risk among hemodialysis patients: a multicenter prospective cohort study

Background

Data are limited on the relationship between waist-to-hip ratio (WHR) and mortality risk among maintenance hemodialysis (MHD) patients. Moreover, the combined association of body mass index (BMI) and WHR with mortality remains uncertain. Therefore, we aimed to explore the individual and combined association of BMI and WHR with the all-cause and cardiovascular disease (CVD) mortality.

Methods

In this multicenter prospective cohort study, we enrolled 1034 MHD patients. The primary outcome was all-cause mortality and secondary outcome was CVD mortality. Multivariable Cox proportional hazards models were used to evaluate the individual and combined association of BMI and WHR with the risk of mortality.

Results

A nonlinear inverse relationship was found between BMI and risk of all-cause mortality (P for nonlinearity <.05). Being underweight (<18.5 kg/m2) was associated with higher all-cause mortality risk (HR 1.45; 95% CI 1.08-1.94) compared with normal weight (18.5-23.9 kg/m2), while being overweight (24-27.9 kg/m2; HR 0.96; 95% CI 0.70-1.31) and obese (≥28 kg/m2; HR 1.19; 95% CI 0.62-2.26) showed no significant differences. Of note, WHR was independently and positively associated with all-cause mortality (per standard deviation increase, HR 1.13; 95% CI 1.00-1.27). When analyzed jointly, patients with low BMI (<18.5 kg/m2) and high WHR (≥0.95) had the highest risk of all-cause mortality. Similar results were obtained for CVD mortality.

Conclusions

In patients undergoing hemodialysis from China, low BMI and high WHR were individually and jointly associated with higher risk of mortality. Our results emphasize that BMI and WHR may jointly affect the prognosis of MHD patients.

Impact of Extremes of Body Mass Index (BMI) in End-Stage Renal Disease (ESRD) Patients

The principal objective of this systematic review is to determine the prognosis of end-stage renal disease (ESRD) patients on maintenance hemodialysis with high body mass index (BMI) and study the potential mechanisms behind it. PubMed and Google Scholar electronic databases covering the period of the last 30 years 1992 to 2022 are searched thoroughly and a total of 11 articles were finally selected for the study. Reference lists of included papers are also searched. Each paper was examined by two independent evaluators who also extracted data from full papers. The quality of the selected studies was assessed by different quality assessment tools and only moderate- to high-quality papers are included.

In this systematic review, we studied different mechanisms explaining the obesity paradox in patients on maintenance hemodialysis, i.e., hemodynamic stability, the concentration of TNF-α receptors, neurohumoral response, role of inflammation, blood pressure, etc. also, the effect of age, gender, duration of treatment, acetyl-ghrelin on obesity paradox have been considered in our paper. This systematic review demonstrates the evidence of an inverse relationship between BMI and all-cause mortality in ESRD patients on maintenance hemodialysis.

In-Hospital Outcomes of Coronary Artery Stenting in Patients With ST-Elevation Myocardial Infarction (STEMI) and Metabolic Syndrome: Insights From the National Inpatient Sample

Background

Metabolic syndrome (MetS) has been recognized as a global health problem. Concurrent MetS diagnosis in patients with ST-elevation myocardial infarction (STEMI) is becoming increasingly common. Given the paucity of studies on the impact of MetS on treatment outcomes in STEMI patients, the purpose of this study was to evaluate in-hospital mortality in STEMI patients with a concurrent MetS diagnosis undergoing a stenting procedure to treat their underlying coronary artery disease.

Method

Patients with or without MetS who underwent coronary stenting following STEMI between 2005 and 2014 were identified from the National Inpatient Sample database. Patients' demographics, comorbidities, and outcomes were compared using a t-test and Pearson's Chi-square test. In addition, 1:1 propensity score matching was performed for age, gender, and race.

Results

Out of 1,938,097 STEMI patients, 5,817 patients with MetS underwent coronary stenting following STEMI and were matched with 5,817 patients with no Mets. MetS group had significantly higher rates of diabetes, hypertension, hyperlipidemia, chronic kidney disease, and obstructive sleep apnea than the no MetS group but lower rates of heart failure and chronic obstructive pulmonary disease. In-hospital mortality following STEMI was significantly lower in patients with MetS (2.5% vs. 7.1%, p<0.001) and remained significant after adjusting for potential confounders (odds ratio (OR) 0.34, 95% confidence interval (95% CI) 0.28-0.42, p<0.0001).

Conclusion

Concurrent diagnosis of MetS among patients undergoing coronary stenting is associated with a decreased in-hospital mortality risk. The impact of specific MetS components on the observed reduction in mortality remains unclear and warrants evaluation in future studies.

Profile of Obesity and Comorbidities and their Correlation among Hemodialysis Patients, Elbasan

INTRODUCTION: Nowadays, obesity is an enormous problem in the public health of undeveloped countries and developing countries. Being overweight, especially obesity in internal organs contributes to increased risk of metabolic and cardiovascular complications in patients with chronic kidney disease. There is no complete data available in our country on the correlation between obesity and comorbidity diseases among persons undergoing dialysis. So we do not know how BMI affects Diabetic or Cardio Vascular Disease (CVD) patients among dialysis patients. We, therefore, undertook this study to evaluate the association of obesity with mobility in hemodialysis patients at the Elbasan dialysis center. METHODOLOGY: This cross-sectional study was performed in 160 patients who have undergone the dialysis process at Elbasan Dialysis Center for three years (2016-2018). A standardized questionnaire was adopted to obtain data from all patients. The subjects were divided a priory into 4 categories based on the body mass index (BMI) (underweight <19, normal 19-25, pre-obese 25-30 and obese ≥30 kg/m2). Software SPSS version 20.0 is used to analyze and evaluate the data. Kaplan-Meier estimate were used to find the correlation between BMI with their prognostic abilities like cardiovascular disease and Diabetes Mellitus Type 2. We have considered statistically significant every p value less than 0.05. RESULT: Over all 160 patients, the men presented the highest number of cases compared to female 73.1% and 26.9% respectively. The mean age resulted 52.7 ± 15.6 years and age groups 50-59 years old and 60-69 years old with 29.4% and 34.3% respectively were the most frequent in this study. About the category of BMI index 8.8% patients resulted underweight, 45% were in normal weight, 28.2% were pre-obese and 6.6% were obese. We observed significant correlations between BMI and some of the demographic data such as: gender, age, place of residence, educational level, smoking and alcohol consumption for p <0.05. Changes in patient survival rates between BMI with DMT2 and cardiovascular disease are not statistically significant (long range p> 0.05). In terms of mortality, a strong significant correlation was observed with the age of 50-69 years and with the index of hemoglobin, urea and creatinine after dialysis with p value <0.05. CONCLUSION: In the paradoxical epidemiology, the overweight becomes chronic on hemodialysis patients and serves as a protective factor which is associated with better survival, but we weren`t found significant association between the BMI and some of the variables analyzed. This study presents a small number of chronic patients on hemodialysis center in Elbasan city. There is a need to better understand the reverse epidemiological causes in individuals on dialysis, which can help us improve the poor outcome in this population.

KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for nutrition in kidney diseases since 1999. Since the publication of the first KDOQI nutrition guideline, there has been a great accumulation of new evidence regarding the management of nutritional aspects of kidney disease and sophistication in the guidelines process. The 2020 update to the KDOQI Clinical Practice Guideline for Nutrition in CKD was developed as a joint effort with the Academy of Nutrition and Dietetics (Academy). It provides comprehensive up-to-date information on the understanding and care of patients with chronic kidney disease (CKD), especially in terms of their metabolic and nutritional milieu for the practicing clinician and allied health care workers. The guideline was expanded to include not only patients with end-stage kidney disease or advanced CKD, but also patients with stages 1-5 CKD who are not receiving dialysis and patients with a functional kidney transplant. The updated guideline statements focus on 6 primary areas: nutritional assessment, medical nutrition therapy (MNT), dietary protein and energy intake, nutritional supplementation, micronutrients, and electrolytes. The guidelines primarily cover dietary management rather than all possible nutritional interventions. The evidence data and guideline statements were evaluated using Grading of Recommendations, Assessment, Development and Evaluation (GRADE) criteria. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

Impact of obesity on the evolution of outcomes in peritoneal dialysis patients

Background

Some studies reveal that obesity is associated with a decrease in mortality in haemodialysis (HD) patients. However, few studies have addressed the association between body mass index (BMI) and peritoneal dialysis (PD) patients.

Methods

We performed this longitudinal, retrospective study to evaluate the impact of obesity on PD patients, using data from the Catalan Registry of Renal Patients from 2002 to 2015 (n = 1573). Obesity was defined as BMI ≥30; low weight: BMI <18.5; normal range: BMI = 18.5–24.99; and pre-obesity: BMI = 25–29.99 kg/m². Variations in BMI were calculated during follow-up. The main outcomes evaluated were the technique and patient survival.

Results

Obesity was observed in 20% of patients starting PD. We did not find differences in sex or PD modality, with the obesity group being older (65.9% are ≥55 years versus 59% non-obese, P = 0.003) and presenting more diabetes mellitus and cardiovascular disease (CVD) (47.9% obese versus 25.1% non-obese and 41.7% versus 31.5%, respectively). We did not observe differences in haemoglobin, albumin and Kt/V in obese patients. Regarding peritonitis rate, we did not find any difference between groups, presenting more peritonitis patients on continuous ambulatory peritoneal dialysis and aged ≥65 years [sub-hazard ratio (SHR) = 1.75, P = 0.000 and SHR = 1.56, P = 0.009]. In relation to technique survival, we found higher transfer to HD in the obese group of patients in the univariate analysis, which was not confirmed in the multivariate analysis (SHR = 1.12, P = 0.4), and we did not find differences in mortality rate. In relation to being transplanted, the underweight group, elderly and patients with CVD or diabetic nephropathy presented less probability to undergo kidney transplantation (SHR = 0.65, 0.24, 0.5 and 0.54, P < 0.05). Obese patients did not present differences in survival with weight changes but in normal-weight patients, a gain of 7% of the basal weight during the first year had a protective effect on death risk (hazard ratio 0.6, P = 0.034).

Conclusions

Obese and non-obese patients starting on PD had similar outcomes.

Comparison of Body Mass Index, Skinfold Thickness, and Bioelectrical Impedance Analysis With Dual-Energy X-Ray Absorptiometry in Hemodialysis Patients

BACKGROUND

Malnutrition is a consistent finding in hemodialysis (HD) patients and is associated with high mortality. The aim was to compare nutrition status indicators using dual-energy x-ray absorptiometry (DXA) as reference in HD patients.

METHODS

Observational cross-sectional study with 42 patients, 55.8 years (±14.6) old, 60% male, HD 2-3 times per week for ≥3 months. HD ranged from 3 months to 28 years (median, 17.3; interquartile range, 8.73-39.0). We used body mass index (BMI) and fat mass (FM) by skinfold thickness (SFT), bioelectrical impedance analysis (BIA), and DXA. Statistical analyses used Bland-Altman plots, Lin's concordance correlation coefficient, the paired t-test, and Pearson or Spearman correlation. P < .05 was significant.

RESULTS

SFT and DXA presented the lowest prevalence of malnutrition (2.4%) and BMI the highest (28.6%). BMI, BIA FM, and SFT FM presented strong positive correlations with DXA FM (r = 0.915; r = 0.976; r = 0.910, P < .001, respectively). BIA FM and fat-free mass (FFM) demonstrated substantial agreement with DXA values (ρ = 0.974 and 0.960, P < .001). Thus, the measurement procedures used, SFT and BIA, underestimated %FM (-4.65% and -2.13%) and overestimated FFM (3.12 kg and 1.0 kg) according to DXA. No differences were found between mean values of BIA FM and DXA (P = .178).

CONCLUSIONS

Compared with DXA, BIA was the most appropriate nutrition indicator for measuring body composition.

Effects of patient age on patency of chronic hemodialysis vascular access

BACKGROUND

In this single-center, retrospective observational study, we assessed the long-term patency of vascular access (VA) after first VA placement to uncover independent risk factors associated with VA patency in Asian hemodialysis (HD) patients stratified by age. We also investigated factors associated with VA patency among older HD patients according to the type of VA in the overall study population.

METHODS

The study period was from January 2011 to December 2013. A total of 651 chronic HD patients with confirmed first upper-extremity VA placement were enrolled, and their records were analyzed retrospectively. A total of 445 patients (68.4%) made up the nonelderly group (< 65 years), and 206 patients (31.6%) were in the elderly group (≥ 65 years). Study outcomes were defined as primary or secondary VA patency.

RESULTS

Autologous arteriovenous fistula (AVF) was more common in the nonelderly group (P <  0.01). Kaplan-Meier curve survival analysis indicated that primary patency was longer in the nonelderly group (P <  0.01); secondary patency, however, was similar between groups (P = 0.37). The multivariate analysis of factors associated with primary VA patency revealed that increased age (hazard ratio [HR], 1.02; 95% confidence interval [CI], 1.01-1.03; P <  0.01) was associated with shorter primary patency, and AVF (HR, 0.38; 95% CI, 0.28-0.51; P <  0.01) was associated with longer primary patency. AVF (HR, 0.57; 95% CI, 0.37-0.87; P = 0.010) and diabetes mellitus (HR, 1.56; 95% CI, 1.07-2.29; P = 0.02) were independently associated with longer and shorter secondary patency periods, respectively; however, increased age was not a risk factor for decreased secondary patency.

CONCLUSIONS

Increased age was associated with shorter primary patency but not secondary patency, whereas AVF placement was associated with longer primary and secondary patency. Considering the similar rates of secondary patency between groups and the superior patency of AVF compared to arteriovenous graft, a fistula-first strategy should be applied to appropriate older patients.

Racial and Ethnic Disparities in the Obesity Paradox

Obesity is a major risk factor for cardiovascular disease and worse survival in the general population. However, in patients with end-stage renal disease (ESRD), higher body mass index and indexes of body fat and muscle are associated with better survival. Furthermore, these associations, which some have described as the obesity paradox, are more consistent in African American patients being treated with hemodialysis when compared with other racial-ethnic groups. This is in view of data indicating that although the rate of progression to ESRD is faster in African American patients, they have a survival advantage after transition to ESRD when compared with their white counterparts. These observations indicate that there may be significant interaction between race/ethnicity and association of body mass index with outcomes in patients with ESRD. In addition, it is possible that mechanisms underlying improved survival in African American hemodialysis patients are partly related to the association of body mass index with outcomes observed in this patient population. Some of these potential mechanisms may include comparatively reduced risk for protein-energy wasting and malnutrition, possible salutary effects of factors that play a role in energy preservation, resistance to deleterious effects of inflammation, and enhanced muscle mass and body composition. Given that ESRD is associated with significantly increased risk for morbidity and mortality, understanding the pathophysiologic mechanisms responsible for the obesity paradox across race-ethnic populations might help identify potential therapeutic targets that can be used to improve survival in this patient population.

Relationship Among Denture Status, Remaining Teeth Number, and Malnutrition in Patients With Chronic Kidney Disease

The purpose of the present study was to evaluate the relationship among the denture status, number of remaining teeth, and malnutrition in patients with chronic kidney disease (CKD). Seventy-three patients (43 men/30 women) who required hemodialysis were included in the study. Weight and height, Kt/V, urea reduction ratio, midweek interdialytic weight gain, ultrafiltration volume, and erythropoietin dosage were determined for all patients. Laboratory measurements and predialysis blood samples for biomarkers were collected within the monthly routine tests. Dental examination focused on the denture status and total number of remaining teeth. Denture status were classified into two groups as prosthesis group (patients have prosthesis) and no prosthesis group (patients do not have any kind of prosthesis). And also, patients were assigned to one of four categories based on the number of remaining natural teeth: (i) edentulous, (ii) 1-7 teeth, (iii) 8-19 teeth, and (iv) >20 teeth. The data were statistically analyzed (a = 0.05). Body mass index values were increased in the prosthesis patients. Serum albumin levels of the CKD patients were under the reference value (3.8 g/dL) both in prosthesis and no prosthesis groups. Patients who have eight and more teeth showed higher serum albumin levels, and patients who had 1-7 teeth showed lower serum albumin levels in prosthesis group. CKD patients' nutritional habits were affected by denture status (having prosthesis or not). The number of the remaining teeth in prosthesis group affected the serum albumin levels of CKD patients.

Body mass index is an independent predictive factor for kidney function evaluated by glomerular filtration rate in a community-dwelling population

BACKGROUND

The effects of overweight and obesity on kidney function have since been identified and become a subject of increased study and concern. But the association between body mass index (BMI) and estimated glomerular filtration rate (eGFR) is not well characterized. The aim of this study was to determine the relationship between BMI and eGFR.

METHODS

To better understand the relationship between BMI and kidney function, we investigated the association between BMI and eGFR using both the baseline BMI level and the follow-up eGFR level and investigated the relationship between the change in BMI and the change in eGFR in 1447 patients from a 4.8-year prospective study in Beijing, People's Republic of China.

RESULTS

In multiple linear regression analysis, age, antihypertensive treatment, and BMI were negatively associated with the follow-up eGFR levels in all participants (R = -0.622, -0.926, and -0.266, respectively; P < 0.05), or in the elderly (R = -0.883, -1.035, and -0.630, respectively; P < 0.05); sex was found to be associated with the follow-up eGFR levels independently not only in all participants (R = 6.783; P < 0.001), but also in the elderly (R = 3.518; P < 0.05). In addition, the change in eGFR levels was positively related to age, the change in LDL-C, the change in TC, and the change in SBP, but negatively related to the change in BMI and the change in HDL-C (all P < 0.05).

CONCLUSIONS

The present study clearly indicated that BMI is an independent predictive factor for kidney function evaluated by the eGFR level during a median 4.8 years of follow-up in Chinese population.

LEVEL OF EVIDENCE

Level III, prospective cohort study.

Relation of Obesity to Outcomes of Hospitalizations for Atrial Fibrillation

Obesity has been linked with increased incidence of atrial fibrillation (AF), but impact of presence of obesity on outcomes of hospitalizations for AF has not been investigated. We used the National Inpatient Sample database 2010 to 2014 to identify all adult hospitalizations aged ≥18years with a primary diagnosis of AF. Obese patients were identified using the co-morbidity variable for obesity, as defined in National Inpatient Sample databases. Multivariable logistic regression was used to compare in-hospital outcomes (mortality, acute stroke events) between obese and non-obese patients with AF. Of 431, 734 hospitalizations for AF, 66,138 (15.3%) were obese. Obese patients were younger and more likely to be African-Americans compared with non-obese patients. Despite being younger, obese patients had significantly higher prevalence of cardiovascular co-morbidities such as hypertension, diabetes mellitus, dyslipidemia, smoking, heart failure, and chronic renal failure (p <0.001 for all). After multivariate risk-adjustment, obese patients had a lower observed in-hospital mortality (0.5% vs 1.0%; unadjusted odds ratio = 0.52, 95% confidence interval [CI] 0.46 to 0.58, p <0.001; adjusted odds ratio = 0.83, 95% CI 0.73 to 0.94, p <0.001) and acute stroke events (0.4% vs 0.7%, unadjusted odds ratio = 0. 65, 95% CI 0.57 to 0.73, p < 0.001; adjusted odds ratio = 0.82, 95% CI 0.72 to 0.94) compared with non-obese patients. In conclusion, in this large retrospective analysis of an unselected nationwide cohort of patients hospitalized for AF, obese patients demonstrated lower risk-adjusted odds of in-hospital mortality and stroke events, consistent with an "obesity paradox."

Time-varying effects of body mass index on mortality among hemodialysis patients: Results from a nationwide Korean registry

Background

Unlike patterns observed in the general population, obesity is associated with better survival among hemodialysis patients, which could be explained by reverse causation or illness-related weight loss. However, the time-varying effect of body mass index (BMI) on hemodialysis survival has not been investigated. Therefore, this study investigated the time-varying effect of BMI on mortality after starting hemodialysis.

Methods

In the present study, we examined Korean Society of Nephrology data from 16,069 adult patients who started hemodialysis during or after the year 2000. Complete survival data were obtained from Statistics Korea. Survival analysis was performed using Cox regression and a non-proportional hazard fractional polynomial model.

Results

During the median follow-up of 8.6 years, 9,272 patients (57.7%) died. Compared to individuals with normal BMI (18.5–24.9 kg/m²), the underweight group (< 18.5 kg/m²) had a higer mortality hazard ratio (HR, 1.292; 95% confidence interval [CI], 1.203–1.387; P < 0.001) and the overweight group (25.0–29.9 kg/m²) had a lower mortality HR (0.904; 95% CI, 0.829–0.985; P = 0.022). The underweight group had increasing HRs during the first 3 to 7 years after starting hemodialysis, which varied according to age group. The young obese group (< 40 years old) had a U-shaped temporal trend in their mortality HRs, which reflected increased mortality after 7 years.

Conclusion

The obese hemodialysis group had better survival during the early post-dialysis period, although the beneficial effect of obesity disappeared 7 years after starting hemodialysis. The young obese group also had an increased mortality HR after 7 years.

Impact of body mass index on short-term and long-term survival in prevalent hemodialysis patients

INTRODUCTION

Numerous studies showed that higher body mass index (BMI) is associated with better survival in hemodialysis (HD) patients. Most of them evaluated short-term mortality. It has been suggested that presence of inflammation may be a key modifier of relationship between BMI and mortality in incident HD patients. We examined whether presence of inflammation modifies the association between BMI and mortality in both short-term and long-term follow-up in a large group of prevalent HD patients.

METHODS

A total of 3.252 HD patients from 41 HD centers were enrolled; the patients were divided into quartiles based on time-averaged BMI (Q1 < 21.5, Q2 21.5 to <24.3, Q3 24.3 to <27.4, Q4 ≥ 27.4 kg/m² ). Inflammation status was defined as present (inflamed) (C-reactive protein (CRP) ≥1.0 mg/dL and/or serum albumin ≤3.5 g/dL) or absent (noninflamed).

FINDINGS

During 7 years of follow-up 1386 patients (42.6%) died. Compared to noninflamed patients, inflamed patients in the lowest BMI quartile showed 5-fold increased risk for mortality in the short-term (95% confidence interval [CI] 2.82-9.22, P < 0.001) and 3-fold in the long-term (95%CI 2.42-4.27, P < 0.001) compared to the highest BMI quartile. Whereas, inflamed patients in the highest BMI quartile experienced 2-fold increased risk in short-term (95%CI 1.17-3.74, P = 0.01) and 1.68-fold increased risk in long-term (95%CI 1.30-2.18, P < 0.001) than in noninflamed patients. The protective effect of BMI for overall mortality was present in all age groups, in both genders, in patient with and without diabetes. BMI was not a mortality predictor in patients with HD duration more than 76 months at baseline. The protective effect of BMI was observed in all albumin tertiles. In patients in the lowest CRP tertile, BMI was not associated with mortality.

DISCUSSION

Higher BMI is associated with lower short-term and long-term mortality risk, especially in patients with inflammation in a prevalent HD population.

Clinical Studies of Interventions to Mitigate Cardiovascular Risk in Peritoneal Dialysis Patients

Cardiovascular disease (CVD) is highly prevalent in the peritoneal dialysis (PD) population, affecting up to 60% of cohorts. CVD is the primary cause of death in up to 40% of PD patients in Australia, New Zealand, and the United States. Cardiovascular mortality rates are reported to be approximately 14 per 100 patient-years, which are 10- to 20-fold greater than those of age- and sex-matched controls. The excess risk of CVD is related to a combination of traditional risk factors (such as hypertension, dyslipidemia, obesity, smoking, sedentary lifestyle, and insulin resistance), nontraditional (kidney disease-related) risk factors (such as anemia, chronic volume overload, inflammation, malnutrition, hyperuricemia, and mineral and bone disorder), and PD-specific risk factors (such as dialysis solutions, glycation end products, hypokalemia, residual kidney function, and ultrafiltration failure). Interventions targeting these factors may mitigate cardiovascular risk, although high-level clinical evidence is lacking. This review summarizes the evidence relating to cardiovascular interventions targeting modifiable CVD risk factors in PD patients, as well as highlighting the key recommendations of the International Society for Peritoneal Dialysis Cardiovascular and Metabolic Guidelines.

The Incidence and Pathophysiology of the Obesity Paradox: Should Peritoneal Dialysis and Kidney Transplant Be Offered to Patients with Obesity and End-Stage Renal Disease?

PURPOSE OF REVIEW

To educate nephrologists and primary-care physicians about the incidence, pathophysiology, and survival benefits of the obesity paradox in end-stage renal disease (ESRD). This review also discusses the future of kidney transplant and peritoneal dialysis in obese dialysis patients.

RECENT FINDINGS

Obesity paradox in ESRD was first reported three decades ago, and since then, there have been several epidemiological studies that confirmed the phenomenon. Regardless of the anthropometric indices used to define obesity in ESRD patients, these markers serve to predict the dialysis patient's survival. The pathophysiology of obesity paradox tends to be multifactorial. Recent cohort studies demonstrated a survival benefit in all race and ethnic groups, but Hispanics and blacks experienced increased survival rates when compared to non-Hispanic whites. Obese dialysis patients should be offered peritoneal dialysis, especially if they are new to dialysis and have an adequate renal residual function. Several studies have shown that the benefit of receiving kidney transplant in obese patients exceeds the risks. The robotic-assisted kidney transplant (RAKT) procedure is the latest innovation that could offer hope for obese dialysis patients who have been denied or are waiting for kidney transplant. The obesity paradox phenomenon in ESRD is a unique illustration of survival benefit in a population that has a high overall annual mortality. Peritoneal dialysis should be encouraged for obese patients who have preserved residual renal function. Kidney transplant centers should encourage RAKT utilization in obese dialysis patients instead of denying them a kidney transplant.

Obesity Paradox in Advanced Kidney Disease: From Bedside to the Bench

While obesity is associated with a variety of complications including diabetes, hypertension, cardiovascular disease and premature death, observational studies have also found that obesity and increasing body mass index (BMI) can be linked with improved survival in certain patient populations, including those with conditions marked by protein-energy wasting and dysmetabolism that ultimately lead to cachexia. The latter observations have been reported in various clinical settings including end-stage renal disease (ESRD) and have been described as the "obesity paradox" or "reverse epidemiology", engendering controversy. While some have attributed the obesity paradox to residual confounding in an effort to "debunk" these observations, recent experimental discoveries provide biologically plausible mechanisms in which higher BMI can be linked to longevity in certain groups of patients. In addition, sophisticated epidemiologic methods that extensively adjusted for confounding have found that the obesity paradox remains robust in ESRD. Furthermore, novel hypotheses suggest that weight loss and cachexia can be linked to adverse outcomes including cardiomyopathy, arrhythmias, sudden death and poor outcomes. Therefore, the survival benefit observed in obese ESRD patients can at least partly be derived from mechanisms that protect against inefficient energy utilization, cachexia and protein-energy wasting. Given that in ESRD patients, treatment of traditional risk factors has failed to alter outcomes, detailed translational studies of the obesity paradox may help identify innovative pathways that can be targeted to improve survival. We have reviewed recent clinical evidence detailing the association of BMI with outcomes in patients with chronic kidney disease, including ESRD, and discuss potential mechanisms underlying the obesity paradox with potential for clinical applicability.

Relationship between Modified Body Mass Index and Prognosis of Renal Amyloid a Amyloidosis

Objectives:

Overhydration occurs in nephrotic syndrome related to kidney involvement of amyloid A (AA) amyloidosis, which can cause an overestimation of body mass index (BMI). Modified BMI (mBMI, albumin×BMI) may be a better marker of nutritional status; therefore, we investigated the relationship between mBMI and the prognosis of patients with renal AA amyloidosis.

Methods:

We retrospectively reviewed the data of patients with biopsy-proven renal AA amyloidosis who were followed up between January 2001 and May 2013. Data regarding baseline characteristics, etiology of amyloidosis, dialysis, and mortality were recorded. Patients were divided into two groups according to median mBMI (group 1, n=60 and group 2, n=61).

Results:

The median age and follow-up period of the cohort (M/F 37/84) were 43 (19) years and 26 (56) months, respectively. Familial Mediterranean fever (37.2%) and tuberculosis (24.8%) were the most common etiologies. The baseline serum creatinine and albumin and proteinuria levels were 1.3 (2.2) mg/dL, 2.6 (1.5) g/dL, and 5.3 (7) g/day, respectively. The mBMIs of groups 1 and 2 were significantly different [41.5 (15.6) vs. 74.2 (21.8) g.kg/m², p =< 0.001]. Group 1 patients had shorter time to dialysis (13.9±20.8 vs. 25.7±28.1 months, p=0.040) and higher mortality (50% vs. 32.7%, p=0.041), whereas the rates of dialysis inception were similar. The area under the curve for mBMI as a predictor of mortality was larger than that for serum albumin and BMI in ROC analysis.

Conclusion:

Lower mBMI has been associated with worse prognosis in renal AA amyloidosis. As an anthropometric measure of nutritional status, mBMI may be a better marker in patients with hypoalbuminemia.

The Relationship between Body Mass Index and Organism-Specific Peritonitis

Background

Obesity is increasingly prevalent worldwide, and a greater number of patients initiate renal replacement therapy with a high body mass index (BMI). This study aimed to evaluate the association between BMI and organism-specific peritonitis.

Methods

All adult patients who initiated peritoneal dialysis (PD) in Australia between January 2004 and December 2013 were included. Data were accessed through the Australia and New Zealand Dialysis and Transplant (ANZDATA) Registry. The co-primary outcomes of this study were time to first organism-specific peritonitis episode, specifically gram-positive, gram-negative, culture-negative, and fungal. Secondary outcomes were individual rates of organism-specific peritonitis for the same 4 microbiological categories.

Results

There were 7,381 peritonitis episodes among the 8,343 incident PD patients evaluated. After multivariable adjustment, obese patients (BMI 30 – 34.9 kg/m2) had an increased risk of fungal peritonitis (adjusted hazard ratio [HR] 1.69, 95% confidence interval [CI] 1.18 – 2.42), very obese patients (BMI ≥ 35 kg/m2) had a significantly higher risk of gram-positive peritonitis (HR 1.15, 95% CI 1.02 – 1.30), while both obese and very obese patients experienced significantly higher risks of gram-negative peritonitis (HR 1.29, 95% CI 1.11 – 1.50 and HR 1.30, 95% CI 1.08 – 1.57, respectively) compared with patients with normal BMI (20 – 24.9 kg/m2). Obesity and severe obesity were independently associated with increased incidence rate ratios of all forms of organism-specific peritonitis with a non-significant trend for severe obesity and gram-negative peritonitis association.

Conclusion

Among Australian patients, obesity and severe obesity are associated with significantly increased rates of gram-positive, gram-negative, fungal, and culture-negative peritonitis.

Longitudinal Weight Change During CKD Progression and Its Association With Subsequent Mortality

BACKGROUND

Few studies have investigated the changes in weight that may occur over time among adults with the progression of chronic kidney disease (CKD). Whether such weight changes are independently associated with death after the onset of end-stage renal disease has also not been rigorously examined.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

We studied 3,933 participants of the Chronic Renal Insufficiency Cohort (CRIC) Study, a longitudinal cohort of patients with CKD. We also performed similar analyses among 1,067 participants of the African American Study of Kidney Disease and Hypertension (AASK).

PREDICTORS

Estimated glomerular filtration rate (eGFR) and weight change during CKD.

OUTCOME

Weight and all-cause mortality after dialysis therapy initiation.

RESULTS

During a median follow-up of 5.7 years in CRIC, weight change was not linear. Weight was stable until cystatin C-based eGFR (eGFRcys) decreased to <35mL/min/1.73m2; thereafter, weight declined at a mean rate of 1.45 kg (95% CI, 1.19-1.70) for every 10 mL/min/1.73m2 decline in eGFRcys. Among the 770 CRIC participants who began hemodialysis or peritoneal dialysis therapy during follow-up, a >5% annualized weight loss after eGFR decreased to <35mL/min/1.73m2 was associated with a 54% higher risk for death after dialysis therapy initiation (95% CI, 1.17-2.03) compared with those with more stable weight (annualized weight changes within 5% of baseline) in adjusted analysis. Similar findings were observed in the AASK.

LIMITATIONS

Inclusion of research participants only; inability to distinguish intentional versus unintentional weight loss.

CONCLUSIONS

Significant weight loss began relatively early during the course of CKD and was associated with a substantially higher risk for death after dialysis therapy initiation. Further studies are needed to determine whether interventions to optimize weight and nutritional status before the initiation of dialysis therapy will improve outcomes after end-stage renal disease.

Frailty and the Quality of Life in Hemodialysis Patients: The Importance of Waist Circumference

OBJECTIVE

Frailty among the end-stage renal disease (ESRD) population is highly prevalent and has been associated with mortality. Little is known about the relation of different aspects of body composition, a modifiable risk factor, with the risk of frailty in ESRD population.

DESIGN AND METHODS

One hundred and fifty-one patients including 85 men and 66 women, aged ≥18 years with ESRD who had been receiving conventional maintenance hemodialysis (HD) for at least 3 months were included. Body fat and muscle mass from both bioimpedance spectroscopy and skin-fold thickness and waist circumference as a surrogate of abdominal obesity were measured. Frailty was defined based on Fried's criteria. Health-related quality of life was collected using the RAND version of the Kidney Disease Quality of Life (KDQOL-36) Survey.

RESULTS

We performed single and multiple predictor logistic regression analyses to determine factors associated with frailty. After adjustment for age, sex, and comorbidities, fat mass (both by bioimpedance spectroscopy and anthropometry) and waist circumference, but not muscle mass remained the main predictors of frailty. The odds ratio of frailty in the third tertile compared with the first was 4.97 (1.70-14.55) and 3.84 (1.39-10.61) for fat mass and waist circumference, respectively (P for trends for both <.05). The scores of physical health and kidney disease effect component of quality of life were lower in frail compared with nonfrail patients (40.7 ± 9.2 vs. 33.7 ± 10.2, P < .01 and 66.8 ± 22.4 vs. 51.6 ± 25.7, P < .05 for physical health and effects of disease, respectively).

CONCLUSIONS

Frailty, which is associated with poor outcomes in chronic HD patients, is common and predicted by fat mass and waist circumference but not by body mass index and muscle mass. Interventions to modify abdominal obesity, reflected by waist circumference, could potentially lower the incidence of frailty and hence improve the quality of life in the HD population.

Comparison of Skinfold Thicknesses and Bioimpedance Spectroscopy to Dual-Energy X-Ray Absorptiometry for the Body Fat Measurement in Patients With Chronic Kidney Disease

BACKGROUND/OBJECTIVES

The aim of the study was to compare the amount of body fat measured by skinfold thickness (SFT) and bioimpedance spectroscopy (BIS) with dual-energy x-ray absorptiometry (DXA) as a reference method.

METHODS

Forty-eight patients undergoing hemodialysis treatment thrice-weekly for at least 3 months (HD group) with a mean age of 59.8 ± 15.5 years, 61 patients with chronic kidney disease (CKD) with an estimated glomerular filtration rate (eGFR) <30 mL/min/1.73 m² and a mean age of 60.1 ± 17.7 years (predialysis group, PreD), and 33 individuals without kidney disease with an eGFR >60 mL/min/1.73 m² and a mean age of 58.7 ± 17.0 years (control group) were included.

RESULTS

Mean percentages of body fat measured by SFT did not significantly differ from those measured by DXA in the HD group ( P = .249) and the PreD group ( P = .355). In the control group, mean percentage of fat mass measured by SFT was significantly higher than measured by DXA ( P = .004). Mean difference was 1.99% ± 3.65%. The measurements of body fat performed by BIS were significantly higher than those performed by DXA in all studied groups ( P < .001). Age was statistically significant and the strongest factor that influenced the variability of measurements obtained by BIS and DXA in all studied groups ( R² = 0.302, 0.153, and 0.250, respectively, for HD, PreD, and control groups).

CONCLUSIONS

SFT as a method of fat mass assessment in daily routine practice seems to be more reliable then BIS in patients treated with hemodialysis and in patients with stage IV/V CKD. However, methods based on bioimpedance techniques can potentially offer more data such as overhydration or an amount of lean tissue mass, but further investigations are needed to establish method the most suitable for patients with CKD.

The Obesity Paradox in Kidney Disease: How to Reconcile it with Obesity Management

Obesity, a risk factor for de novo chronic kidney disease (CKD), confers survival advantages in advanced CKD. This so-called obesity paradox is the archetype of the reverse epidemiology of cardiovascular risks, in addition to the lipid, blood pressure, adiponectin, homocysteine, and uric acid paradoxes. These paradoxical phenomena are in sharp contradistinction to the known epidemiology of cardiovascular risks in the general population. In addition to advanced CKD, the obesity paradox has also been observed in heart failure, chronic obstructive lung disease, liver cirrhosis, and metastatic cancer, as well as in the elderly. These are populations in whom protein-energy wasting and inflammation are strong predictors of early death. Both larger muscle mass and higher body fat provide longevity in these patients, whereas thinner body habitus and weight loss are associated with higher mortality. Muscle mass appears to be superior to body fat in conferring an even greater survival. The obesity paradox may be the result of a time discrepancy between competing risk factors, i.e., overnutrition as the long-term killer versus undernutrition as the short-term killer. Hemodynamic stability of obesity, lipoprotein defense against circulating endotoxins, protective cytokine profiles, toxin sequestration of fat mass, and antioxidation of muscle may play important roles. Despite claims that obesity paradox is a statistical fallacy and a result of residual confounding, the consistency of data and other causality clues suggest a high biologic plausibility. Examining the causes and consequences of the obesity paradox may help discover important pathophysiologic mechanisms leading to improved outcomes in patients with CKD.

Association of Growth Differentiation Factor 15 with Mortality in a Prospective Hemodialysis Cohort

BACKGROUND/AIMS

Cardiovascular disease and protein-energy wasting are among the strongest predictors of the high mortality of dialysis patients. In the general population, the novel cardiovascular and wasting biomarker, growth differentiation factor 15 (GDF15), is associated with decreased survival. However, little is known about GDF15 in dialysis patients.

METHODS

Among prevalent hemodialysis patients participating in a prospective study (October 2011 to August 2015), we examined the association of baseline GDF15 levels with all-cause mortality using unadjusted and case mix-adjusted death hazard ratios (HRs) that controlled for age, sex, race, ethnicity, diabetes, and dialysis vintage.

RESULTS

The mean age ± SD of the 203 patients included in the study was 53.2 ± 14.5 years, and the cohort included 41% females, 34% African-Americans, and 48% Hispanics. GDF15 levels (mean ± SD 5.94 ± 3.90 ng/mL; range 1.58-39.8 ng/mL) were higher among older patients and were inversely associated with serum creatinine concentrations as a surrogate for muscle mass. Each 1.0 ng/mL increase in GDF15 was associated with an approximately 17-18% higher mortality risk in the unadjusted and case mix models (p < 0.05). Increments of about 1 SD (a 4.0 ng/mL increase in GDF15) were associated with a nearly 2-fold higher death risk. The highest GDF15 tertile was associated with higher mortality risk (reference: lowest tertile): the HRs (95% CI) were 3.19 (1.35-7.55) and 2.45 (1.00-6.00) in the unadjusted and the case mix-adjusted model, respectively. These incremental death trends were confirmed in cubic spline models.

CONCLUSION

Higher circulating GDF15 levels are associated with higher mortality risk in hemodialysis patients. Future studies are needed to determine whether GDF15 may represent a novel therapeutic target for cardiovascular disease, wasting, and death in this population.

Nutrition, vitamin D, and health outcomes in hemodialysis: time for a feeding frenzy?

PURPOSE OF REVIEW

The role of nutrition and nutritional supplementation in dialysis recently has been reinvigorated, with small clinical trials exploring surrogate outcomes and larger epidemiologic studies generating treatment hypotheses requiring further study. The present review focuses on major aspects of nutrition and outcomes in hemodialysis patients: protein and calorie intake and nutritional vitamin D supplementation.

RECENT FINDINGS

Building on data from small studies, two large, quasi-experimental cohort studies showed significant mortality benefits associated with oral nutritional supplements provided during dialysis, suggesting potential options for ameliorating the protein-energy wasting that is common in dialysis patients and associated with poor outcomes. Multiple cohort studies suggest, both in the general population and in dialysis, that higher 25(OH) vitamin D levels are associated with improved outcomes; however, no major mortality trials exist in dialysis, and the smaller, surrogate studies conducted to date have been disappointing, showing no consistent benefits in surrogate outcomes including inflammation and anemia, despite appropriate responses of vitamin D levels to repletion.

SUMMARY

Nutritional interventions are attractive options for improving outcomes in dialysis patients. Nutritional protein supplements have considerable promise, but require further study, preferably in a large, generalizable pragmatic trial. Small nutritional vitamin D supplementation trials in dialysis have had disappointing results. In the absence of new data, there appears to be no role for routine assessment or repletion of 25(OH) vitamin D deficiency or insufficiency in dialysis.

Obese and diabetic patients with end-stage renal disease: Peritoneal dialysis or hemodialysis?

Obesity is a chronic disease that is increasingly prevalent around the world and is a well-recognized risk factor for type 2 diabetes and hypertension, leading causes of end-stage renal disease (ESRD). The obese diabetic patient with ESRD is a challenge for the nephrologist with regard to the type of renal replacement therapy that should be suggested and offered to the patient. There is no evidence that either peritoneal dialysis or hemodialysis is contraindicated in obese ESRD patients. In the literature, we can find a discrepancy in the impact of obesity on mortality among hemodialysis vs. peritoneal dialysis patients. Several studies in hemodialysis patients suggest that a higher BMI confers a survival advantage - the so-called "reverse epidemiology". In contrast, the literature among obese peritoneal dialysis patients is inconsistent, with various studies reporting an increased risk of death, no difference, or a decreased risk of death. Many of these studies only spanned across a few years, and this is probably too short of a time frame for a realistic assessment of obesity's impact on mortality in ESRD patients. The decision for dialysis modality in an obese diabetic patient with ESRD should be individualized. According to the results of published studies, we cannot suggest PD or HD as a better solution for all obese diabetic patients. The obese patient should be educated about all their dialysis options, including home dialysis therapies. In this review, the available literature related to the dialysis modality in obese patients with diabetes and ESRD was reviewed.

Serum Creatinine Modifies Associations between Body Mass Index and Mortality and Morbidity in Prevalent Hemodialysis Patients

Background

High body mass index (BMI) is paradoxically associated with better outcomes in hemodialysis (HD) patients. This study aimed to examine whether serum creatinine (Cr), a marker of muscle mass, could modify the association between BMI, and mortality and morbidity in prevalent HD patients.

Methods

A retrospective study was conducted using a nationwide database from the registry of the Japanese Society for Dialysis Therapy. A total of 119,099 patients were selected (age: 65±12 years; median time on HD: 5.6 years; male: 62%), and we examined the association of basal BMI with mortality and morbidity after a 1-year period. Patients were stratified either by BMI into 4 groups or by serum Cr levels into 3 tertiles. Odds ratio (OR) [95% confidence interval] was calculated by multivariate logistic regression analysis.

Results

Higher BMI did not predict a higher 1-year total mortality. However, when we stratified the patients by serum Cr levels, the risk of cardiac death became significantly higher in obese patients with the lowest Cr levels, in both males (OR 2.82 [1.51–5.27], p<0.01) and females (OR 2.00 [1.03–3.90], p<0.05). The risk of new cerebral infarction was also higher in obese male patients within the lowest Cr tertile. In contrast, there was a significantly lower risk of cardiac, cerebrovascular, and infection-related death in non-obese patients with higher levels of Cr. Higher serum Cr was also related to a lower risk of cardiovascular events and hip fracture in non-obese HD patients.

Conclusions

The obesity paradox was found to be present in HD patients only when obesity was defined by BMI. Decreased serum Cr levels were found to be positively associated with clinical poor outcomes in all BMI groups. Thus, irrespective of BMI, the evaluation of serum Cr levels is important to predict mortality and morbidity in patients receiving regular HD.

Lean Body Mass and Survival in Hemodialysis Patients and the Roles of Race and Ethnicity

BACKGROUND

Lean body mass (LBM) represents the "fat-free" muscle mass in hemodialysis (HD) patients and is an important nutritional measure. Previous studies have found that both higher LBM and body mass index (BMI) were related to greater survival in HD patients. Additional studies have shown differences in survival across racial-ethnic groups of HD patients. However, the association of LBM and mortality across racial-ethnic subgroups has not been examined.

OBJECTIVE

We hypothesize that racial differences in LBM affect the mortality in HD patients.

SETTING AND SUBJECTS

Chronic HD patients from a large dialysis organization in the United States.

PREDICTORS

Estimated LBM (eLBM), self-identified racial subgroups.

MAIN OUTCOME MEASURE

5-year survival.

STUDY DESIGN

We examined the association between baseline eLBM and survival using Cox proportional hazard models adjusted for demographics, comorbidities, and laboratory measures. Associations were examined across subgroups of race-ethnicity (non-Hispanic white, African American, and Hispanic) and BMI.

RESULTS

The final cohort included 117,683 HD patients, who were 62 ± 15 (mean ± standard deviation) years old, 43% women and 59% with diabetes mellitus. Higher eLBM was linearly associated with lower mortality. Compared with the reference group (48.4-<50.5 kg), patients with the lowest eLBM (<41.3 kg) had a 1.4-fold higher risk of mortality (hazard ratio: 1.37; 95% confidence interval: 1.30-1.44) in the fully adjusted model. A similar linear association was seen among patients with BMI < 35 kg/m(2) and in non-Hispanic whites and African American subgroups. However, higher eLBM was not associated with improved survival in Hispanic patients or patients with BMI ≥ 35 kg/m(2).

LIMITATION

Potential residual confounding.

CONCLUSIONS

Higher eLBM is associated with a lower mortality risk in HD patients, especially among non-Hispanic white and African American groups. Hispanic patients do not demonstrate a similar inverse relationship. The association between LBM and mortality among different racial groups of HD patients deserves additional study.

Body Composition Affects Urea Distribution Volume Estimated by Watson's Formula

OBJECTIVE

Dialysis machines use the Watson formula (Vwatson) to estimate the urea distribution volume (UDV) to calculate the online Kt/V for each dialysis session. However, the equation could give rise to inaccuracies. The present study analyzes whether body composition affects UDV estimated by Vwatson in comparison to bioimpedance spectroscopy (Vbis) as the reference method.

DESIGN

This is a transversal study performed in the setting of a hemodialysis unit.

SUBJECTS

Prevalent hemodialysis patients.

INTERVENTION

The same day, UDV was measured using Vwatson and Vbis. We compared their results.

MAIN OUTCOME MEASURE

Differences between UDV using Watson equation and Vbis.

RESULTS

We included 144 prevalent patients. Vwatson overestimated the volume with regard to Vbis (Vwatson - Vbis) by 2.5 L (1.8 L; P = .001). We found an excellent correlation between the 2 methods. A higher mean Vwatson - Vbis value was correlated to older age (P = .03), body mass index (P = .01), fat tissue index (P = .001), lower lean tissue index (P = .001), lower extracellular water (P = .01), and intracellular water (P = .001).

CONCLUSION

Body composition affects UDV estimated by Vwatson, thus modifying the result of Kt/V. In young patients who present more lean tissue and less fat tissue, Kt/V is underestimated with Vwatson.

Risk Adjustment and the Assessment of Disparities in Dialysis Mortality Outcomes

Standardized mortality ratios (SMRs) reported by Medicare compare mortality at individual dialysis facilities with the national average, and are currently adjusted for race. However, whether the adjustment for race obscures or clarifies disparities in quality of care for minority groups is unknown. Cox model-based SMRs were computed with and without adjustment for patient race for 5920 facilities in the United States during 2010. The study population included virtually all patients treated with dialysis during this period. Without race adjustment, facilities with higher proportions of black patients had better survival outcomes; facilities with the highest percentage of black patients (top 10%) had overall mortality rates approximately 7% lower than expected. After adjusting for within-facility racial differences, facilities with higher proportions of black patients had poorer survival outcomes among black and non-black patients; facilities with the highest percentage of black patients (top 10%) had mortality rates approximately 6% worse than expected. In conclusion, accounting for within-facility racial differences in the computation of SMR helps to clarify disparities in quality of health care among patients with ESRD. The adjustment that accommodates within-facility comparisons is key, because it could also clarify relationships between patient characteristics and health care provider outcomes in other settings.

The impact of social disadvantage in moderate-to-severe chronic kidney disease: an equity-focused systematic review*

It is unclear whether a social gradient in health outcomes exists for people with moderate-to-severe chronic kidney disease (CKD). We critically review the literature for evidence of social gradients in health and investigate the ‘suitability’ of statistical analyses in the primary studies. In this equity-focused systematic review among adults with moderate-to-severe CKD, factors of disadvantage included gender, race/ethnicity, religion, education, socio-economic status or social capital, occupation and place of residence. Outcomes included access to healthcare, kidney disease progression, cardiovascular events, all-cause mortality and suitability of analyses. Twenty-four studies in the pre-dialysis population and 34 in the dialysis population representing 8.9 million people from 10 countries were included. In methodologically suitable studies among pre-dialysis patients, a significant social gradient was observed in access to healthcare for those with no health insurance and no home ownership. Low income and no home ownership were associated with higher cardiovascular event rates and higher mortality [HR 1.94, 95% confidence interval (CI) 1.27–2.98; HR 1.28, 95% CI 1.04–1.58], respectively. In methodologically suitable studies among dialysis patients, females, ethnic minorities, those with low education, no health insurance, low occupational level or no home ownership were significantly less likely to access cardiovascular healthcare than their more advantaged dialysis counterparts. Low education level and geographic remoteness were associated with higher cardiovascular event rates and higher mortality (HR 1.54, 95% CI 1.01–2.35; HR 1.21, 95% CI 1.08–1.37), respectively. Socially disadvantaged pre-dialysis and dialysis patients experience poorer access to specialist cardiovascular health services, and higher rates of cardiovascular events and mortality than their more advantaged counterparts.

Neighborhood socioeconomic status, race, and mortality in young adult dialysis patients

Young blacks receiving dialysis have an increased risk of death compared with whites in the United States. Factors influencing this disparity among the young adult dialysis population have not been well explored. Our study examined the relation of neighborhood socioeconomic status (SES) and racial differences in mortality in United States young adults receiving dialysis. We merged US Renal Data System patient-level data from 11,027 black and white patients ages 18-30 years old initiating dialysis between 2006 and 2009 with US Census data to obtain neighborhood poverty information for each patient. We defined low SES neighborhoods as those neighborhoods in U.S. Census zip codes with ≥20% of residents living below the federal poverty level and quantified race differences in mortality risk by level of neighborhood SES. Among patients residing in low SES neighborhoods, blacks had greater mortality than whites after adjusting for baseline demographics, clinical characteristics, rurality, and access to care factors. This difference in mortality between blacks and whites was significantly attenuated in higher SES neighborhoods. In the United States, survival between young adult blacks and whites receiving dialysis differs by neighborhood SES. Additional studies are needed to identify modifiable factors contributing to the greater mortality among young adult black dialysis patients residing in low SES neighborhoods.

Oral active vitamin d treatment and mortality in maintenance hemodialysis patients

AIMS

To analyze the relationship between oral active vitamin D treatment and mortality in maintenance hemodialysis (MHD) patients.

METHODS

We examined the association of oral calcitriol treatment with mortality in 156 MHD patients (80 men and 76 women; mean age: 59 ± 15 years). The survival analysis of all-cause and cardiovascular mortality was performed using the Kaplan-Meier survival and Cox proportional-hazards analyses.

RESULTS

In all, 108 of the 156 patients received active vitamin D treatment. The intact parathyroid hormone level was obviously lower in the patients who received active vitamin D treatment than in those who did not. Throughout the whole follow-up, overall mortality was 16.7% (26 deaths, 13 in each group). The cardiovascular mortality rates were 14.6% (8/48) in the control group and 4.6% (5/108) in the calcitriol group. The crude analysis of all-cause and cardiovascular mortality using the Kaplan-Meier curve showed a significant reduction in mortality risk for patients who received oral active vitamin D compared with those who did not receive it (p = 0.015 and 0.026, respectively). Cox's regression analysis showed that active vitamin D treatment was associated with a significantly lower risk of all-cause mortality (RR = 0.399, 95% CI 0.185-0.862, p = 0.019) and cardiovascular mortality (RR = 0.295, 95% CI 0.094-0.93, p = 0.037). However, after adjusting for potential confounding variables, oral active vitamin D therapy was no longer clearly associated with a lower risk of either all-cause or cardiovascular mortality.

CONCLUSION

Oral active vitamin D treatment was associated with improved survival in MHD patients. However, this survival benefit was smaller than previously reported, and a large cohort study should be performed.

Body mass index and mortality in patients on maintenance hemodialysis: a meta-analysis

PURPOSE

In patients undergoing maintenance hemodialysis (MHD), increasing numbers of studies have reported a reduced mortality in patients with an increased body mass index (BMI). This article provides a meta-analysis on the assessment of the relationship between BMI and mortality in MHD patients.

METHODS

A systemic literature review was conducted to identify studies that examined all-cause mortality, with or without cardiovascular events, on the basis of bodyweight or obesity measures in MHD population published before October 2012.

RESULTS

Eight observational studies with a total of 190,163 patients were included. Compared to the individuals with a normal BMI, overweight patients and obese patients were associated with lower all-cause mortality [relative risk (RR) 0.86, 95% confidence interval (CI) 0.84-0.88; RR 0.77, 95% CI 0.75-0.78, respectively] and cardiovascular mortality (RR 0.86; 95% CI 0.81-0.91; RR 0.78, 95% CI 0.73-0.83, respectively). Underweight patients had relatively higher all-cause and cardiovascular mortality (RR 1.22, 95% CI 1.20-1.25; RR 1.19, 95% CI 1.11-1.28, respectively). In an obesity-stratified analysis, the patients with moderate or severe obesity presented a strongly decreased all-cause mortality risk (RR 0.64, 95% CI 0.61-0.68) and cardiovascular mortality risk (RR 0.63, 95% CI 0.53-0.75) compared to patients with mild obesity (RR 0.74, 95% CI 0.71-0.77; RR 0.81, 95% CI 0.75-0.87, respectively).

CONCLUSIONS

These findings show that overweight and obese patients have lower all-cause and cardiovascular mortality rates in patients undergoing MHD. Body weight management and optimized nutritional and metabolic support should help to reduce the high mortality rates that are prevalent in the hemodialysis population.

Relationship between changes in body fat and a decline of renal function in the elderly

Obesity is a risk factor for chronic kidney disease, and its prevalence among the elderly is increasing. We investigated the effects of changes in body fat percentage (BFP) on the longitudinal changes in the estimated glomerular filtration rate (eGFR) in the elderly. This prospective cohort study included 390 participants aged >65 years who underwent bioelectrical impedance analysis at baseline and follow-up as a part of the Korean Longitudinal Study on Health and Aging. After a median follow-up period of 5.3 years, BFP was significantly higher than that at the start point (P<0.05). Participants who had the largest increase in BFP had the highest BMI and waist circumference (WC) (P<0.001). The highest tertile had the highest white blood cell count and erythrocyte sedimentation rate, incidence of rapid progression, and decline in eGFR >25% (P≤0.017, P = 0.025, P = 0.005, respectively). The lowest tertile had the lowest triglyceride and highest high-density lipoprotein levels (P<0.05). The adjusted decline rate in eGFR was correlated with a change in BFP (P = 0.039), but not with that in BMI or WC. The highest tertile had a 4.875-fold increase in the risk for rapid progression to a decline in eGFR (95% CI: 1.366-17.397) and a 4.931-fold decrease in the risk to a decline in eGFR>25% (95% CI: 1.617-15.037), when compared with the lowest tertile. In subgroup analysis, the incidence of renal outcomes was significantly increased according to the increase in BFP in patients with lower eGFR (P≤0.010). A change in BFP may be associated with inflammation and dyslipidemia development, and longitudinal changes in body fat are related to a decrease in eGFR in the elderly.

Obesity in CKD--what should nephrologists know?

Obesity, the epidemic of the 21st century, carries a markedly increased risk for comorbid complications, such as type 2 diabetes, cancer, hypertension, dyslipidemia, cardiovascular disease, and sleep apnea. In addition, obesity increases the risk for CKD and its progression to ESRD. Paradoxically, even morbid obesity associates with better outcomes in studies of ESRD patients on maintenance dialysis. Because the number of obese CKD and maintenance dialysis patients is projected to increase markedly in developed as well as low- and middle-income countries, obesity is a rapidly emerging problem for the international renal community. Targeting the obesity epidemic represents an unprecedented opportunity for health officials to ameliorate the current worldwide increase in CKD prevalence. Nephrologists need more information about assessing and managing obesity in the setting of CKD. Specifically, more precise estimation of regional fat distribution and the amount of muscle mass should be introduced into regular clinical practice to complement more commonly used practical markers, such as body mass index. Studies examining the effects of obesity on kidney disease progression and other clinical outcomes along with weight management strategies are much needed in this orphan area of research.

Effect of age and dialysis vintage on obesity paradox in long-term hemodialysis patients

BACKGROUND

In contrast to the general population, higher body mass index (BMI) is associated with greater survival in patients receiving hemodialysis (HD; "obesity paradox"). We hypothesized that this paradoxical association between BMI and death may be modified by age and dialysis vintage.

STUDY DESIGN

Retrospective observational study using a large HD patient cohort.

SETTING & PARTICIPANTS

123,383 maintenance HD patients treated in DaVita dialysis clinics between July 1, 2001, and June 30, 2006, with follow-up through September 30, 2009.

PREDICTORS

Age, dialysis vintage, and time-averaged BMI. Time-averaged BMI was divided into 6 subgroups; <18.5, 18.5-<23.0, 23.0-<25.0, 25.0-<30.0, 30.0-<35.0, and ≥35.0kg/m(2). BMI category of 23-<25kg/m(2) was used as the reference category.

OUTCOMES

All-cause, cardiovascular, and infection-related mortality.

RESULTS

Mean BMI of study participants was 27±7kg/m(2). Time-averaged BMI was <18.5 and ≥35kg/m(2) in 5% and 11% of patients, respectively. With progressively higher time-averaged BMI, there was progressively lower all-cause, cardiovascular, and infection-related mortality in patients younger than 65 years. In those 65 years or older, even though overweight/obese patients had lower mortality compared with underweight/normal-weight patients, sequential increases in time-averaged BMI > 25kg/m(2) added no additional benefit. Based on dialysis vintage, incident HD patients had greater all-cause and cardiovascular survival benefit with a higher time-averaged BMI compared with the longer term HD patients.

LIMITATIONS

Causality cannot be determined, and residual confounding cannot be excluded given the observational study design.

CONCLUSIONS

Higher BMI is associated with lower death risk across all age and dialysis vintage groups. This benefit is more pronounced in incident HD patients and those younger than 65 years. Given the robustness of the survival advantage of higher BMI, examining interventions to maintain or even increase dry weight in HD patients irrespective of age and vintage are warranted.

Obesity paradox in end-stage kidney disease patients

In the general population, obesity is associated with increased cardiovascular risk and decreased survival. In patients with end-stage renal disease (ESRD), however, an "obesity paradox" or "reverse epidemiology" (to include lipid and hypertension paradoxes) has been consistently reported, i.e. a higher body mass index (BMI) is paradoxically associated with better survival. This survival advantage of large body size is relatively consistent for hemodialysis patients across racial and regional differences, although published results are mixed for peritoneal dialysis patients. Recent data indicate that both higher skeletal muscle mass and increased total body fat are protective, although there are mixed data on visceral (intra-abdominal) fat. The obesity paradox in ESRD is unlikely to be due to residual confounding alone and has biologic plausibility. Possible causes of the obesity paradox include protein-energy wasting and inflammation, time discrepancy among competitive risk factors (undernutrition versus overnutrition), hemodynamic stability, alteration of circulatory cytokines, sequestration of uremic toxin in adipose tissue, and endotoxin-lipoprotein interaction. The obesity paradox may have significant clinical implications in the management of ESRD patients especially if obese dialysis patients are forced to lose weight upon transplant wait-listing. Well-designed studies exploring the causes and consequences of the reverse epidemiology of cardiovascular risk factors, including the obesity paradox, among ESRD patients could provide more information on mechanisms. These could include controlled trials of nutritional and pharmacologic interventions to examine whether gain in lean body mass or even body fat can improve survival and quality of life in these patients.

Low protein nitrogen appearance as a surrogate of low dietary protein intake is associated with higher all-cause mortality in maintenance hemodialysis patients

To determine the association between all-cause mortality and dietary protein intake in patients with chronic kidney disease, we performed a large-scale, 8-y prospective cohort study in 98,489 maintenance hemodialysis patients from a multicenter dialysis care provider. Compared with the reference level (60 to <70 g/d), low protein nitrogen appearance (PNA) levels [<30 g/d, HR: 1.40 (95% CI: 1.30, 1.50); 30 to <40 g/d, HR: 1.33 (95% CI: 1.28, 1.39)] was associated with higher all-cause mortality, and high PNA levels [≥110 g/d, HR: 0.92 (95% CI: 0.88, 0.97); 100 to <110 g/d, HR: 0.87 (95% CI: 0.82, 0.91)] were associated with lower all-cause mortality in all analyses. This association was also found in subanalyses performed among racial and hypoalbuminemic groups. Hence, using PNA as a surrogate for protein intake, a low daily dietary protein intake is associated with increased risk of death in all hemodialysis patients. Whether the association between dietary protein intake and survival is causal or a consequence of anorexia secondary to protein-energy-wasting/inflammation or other factors should be explored in interventional trials.

Patient care staffing levels and facility characteristics in U.S. hemodialysis facilities

BACKGROUND

Higher numbers of registered nurses (RNs) per patient have been associated with improved patient outcomes in acute-care facilities. Variation in and associations of patient care staffing levels and hemodialysis facility characteristics have not been examined previously.

STUDY DESIGN

Cross-sectional study using Poisson regression to examine associations between patient care staffing levels and hemodialysis facility characteristics.

SETTING & PARTICIPANTS

4,800 US hemodialysis facilities in the 2009 Centers for Medicare & Medicaid (CMS) End-Stage Renal Disease Annual Facility Survey (CMS-2744 form).

PREDICTORS

Facility characteristics, including profit status, freestanding status, chain affiliation, and geographic region, adjusted for facility size, capacity, functional type, and urbanicity.

OUTCOMES

Patient care staffing levels, including ratios of RNs, licensed practical nurses (LPNs), patient care technicians (PCTs), composite staff (RN + LPN + PCT), social workers, and dietitians to in-center hemodialysis patients.

RESULTS

After adjusting for background facility characteristics, ratios of RNs and LPNs to patients were 35% (P < 0.001) and 42% (P < 0.001) lower, respectively, but the PCT to patient ratio was 16% (P < 0.001) higher in for-profit than nonprofit facilities (rate ratios of 0.65 [95% CI, 0.63-0.68], 0.58 [95% CI, 0.51-0.65], and 1.16 [95% CI, 1.12-1.19], respectively). Regionally, compared to the Northeast, the adjusted RN to patient ratio was 14% (P < 0.001) lower in the Midwest, 25% (P < 0.001) lower in the South, and 18% (P < 0.001) lower in the West. Even after additional adjustments, the large for-profit chains had significantly lower RN and LPN to patient ratios than the largest nonprofit chain, but a significantly higher PCT to patient ratio. Overall composite staffing levels also were lower in for-profit and chain-affiliated facilities. The patterns hold when hospital-based units were excluded.

LIMITATIONS

Nursing hours were not available. Two part-time staff were counted as one full-time equivalent, which may not always be accurate.

CONCLUSIONS

The significant variation in patient care staffing levels and its associations with facility characteristics warrants inclusion in future large-scale hemodialysis outcomes studies. End-stage renal disease networks and hemodialysis facilities should attend to quality assurance and performance improvement initiatives that maximize licensed nurse staffing levels in hemodialysis facilities.

Mortality predictability of body size and muscle mass surrogates in Asian vs white and African American hemodialysis patients

OBJECTIVE

To determine whether the association of body size and muscle mass with survival among patients undergoing long-term hemodialysis (HD) is consistent across race, especially in East Asian vs white and African American patients.

PATIENTS AND METHODS

Using data from 20,818 patients from South Korea who underwent HD from February 1, 2001, to June 30, 2009, and 20,000 matched patients from the United States (10,000 whites and 10,000 African Americans) who underwent HD from July 1, 2001, to June 30, 2006, we compared mortality associations of baseline body mass index (BMI) and serum creatinine level as likely surrogates of obesity and muscle mass across the 3 races.

RESULTS

In Korean HD patients, higher BMI together with higher serum creatinine levels were associated with greater survival, as previously reported from US and European studies. In the matched cohort (10,000 patients from each of the 3 races), mortality risks were lower across higher BMI and serum creatinine levels, and these associations were similar in all 3 races (reference groups: patients with BMI >25.0 kg/m(2) or serum creatinine >12 mg/dL in each race). White, African American, and Korean patients with BMI levels of 18.5 kg/m(2) or less (underweight) had 78%, 79%, and 57% higher mortality risk, respectively, and white, African American, and Korean patients with serum creatinine levels of 6.0 mg/dL or less had 108%, 87%, and 78% higher mortality, respectively.

CONCLUSION

This study shows that race does not modify the association of higher body size and muscle mass with greater survival in HD patients. Given the consistency of the obesity paradox, which may be related to a mitigated effect of protein-energy wasting on mortality irrespective of racial disparities, nutritional support to improve survival should be tested in HD patients of all races.

Association of serum phosphorus concentration with mortality in elderly and nonelderly hemodialysis patients

OBJECTIVE

Hypo- and hyperphosphatemia have each been associated with increased mortality in maintenance hemodialysis (MHD) patients. There has not been previous evaluation of a differential relationship between serum phosphorus level and death risk across varying age groups in MHD patients.

DESIGN AND SETTINGS

In a 6-year cohort of 107,817 MHD patients treated in a large dialysis organization, we examined the association between serum phosphorus levels with all-cause and cardiovascular mortality within 5 age categories (15 to <45, 45 to <65, 65 to <70, 70 to <75, and ≥75 years old) using Cox proportional hazards models adjusted for case-mix covariates and malnutrition inflammation complex syndrome (MICS) surrogates.

MAIN OUTCOME MEASURE

All-cause and cardiovascular mortality.

RESULTS

The overall mean age of the cohort was 60 ± 16 years, among whom there were 45% women, 35% Blacks, and 58% diabetics. The time-averaged serum phosphorus level (mean ± SD) within each age category was 6.26 ± 1.4, 5.65 ± 1.2, 5.26 ± 1.1, 5.11 ± 1.0, and 4.88 ± 1.0 mg/dL, respectively (P for trend <.001). Hyperphosphatemia (>5.5 mg/dL) was consistently associated with increased all-cause and cardiovascular mortality risks across all age categories, including after adjustment for case-mix and MICS-related covariates. In fully adjusted models, a low serum phosphorus level (<3.5 mg/dL) was associated with increased all-cause mortality only in elderly MHD patients ≥65 years old (hazard ratio [95% confidence interval]: 1.21 [1.07-1.37], 1.13 [1.02-1.25], and 1.28 [1.2-1.37] for patients 65 to <70, 70 to <75, and ≥75 years old, respectively), but not in younger patients (<65 years old). A similar differential cardiovascular mortality risk for low serum phosphorus levels between old and young age groups was observed.

CONCLUSIONS

The association between hyperphosphatemia and mortality is similar across all age groups of MHD patients, whereas hypophosphatemia is associated with increased mortality only in elderly MHD patients. Preventing very low serum phosphorus levels in elderly dialysis patients may be associated with better outcomes, which needs to be examined in future studies.