Reverse epidemiology in peritoneal dialysis patients: the Canadian experience and review of the literature

Peritoneal dialysis patient selection from a comorbidity perspective

Despite many medical and socioeconomic advantages, peritoneal dialysis (PD) is an underutilized dialysis modality that in most countries is used by only 5%-20% of dialysis patients, while the vast majority are treated with in-center hemodialysis. Several factors may explain this paradox, such as lack of experience and infrastructure for training and monitoring of PD patients, organizational issues, overcapacity of hemodialysis facilities, and lack of economic incentives for dialysis centers to use PD instead of HD. In addition, medical conditions that are perceived (rightly or wrongly) as contraindications to PD represent barriers for the use of PD because of their purported potential negative impact on clinical outcomes in patients starting PD. While there are few absolute contraindications to PD, high age, comorbidities such as diabetes mellitus, obesity, polycystic kidney disease, heart failure, and previous history of abdominal surgery and renal allograft failure, may be seen (rightly or wrongly) as relative contraindications and thus barriers to initiation of PD. In this brief review, we discuss how the presence of these conditions may influence the strategy of selecting patients for PD, focusing on measures that can be taken to overcome potential problems.

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.

Association of Body Mass Index and Outcome in Acutely Ill Patients With Chronic Kidney Disease Requiring Intensive Care Therapy

OBJECTIVE

An association of body mass index (BMI) and outcome, the "obesity paradox," has been described in patients with chronic kidney disease (CKD) and end-stage renal disease. We sought to assess whether a potential beneficial effect of a high body mass is also seen in CKD patients with critical illness.

METHODS

In a retrospective analysis of a prospectively collected database of 123,416 patients from 107 Austrian intensive care units (ICUs) in whom BMI was available, the association of 6 groups of BMI and hospital mortality was assessed in 12,206 patients with CKD 3-5 by univariate and multivariate logistic regression analyses.

RESULTS

Patients with CKD were sicker, had a longer ICU stay, and had a higher ICU and hospital mortality than those without. The association of BMI and outcome in CKD patients indicated a U-shaped curve with the highest mortality in patients with BMI <20 and ≥40, and the lowest with a BMI between ≥25 and <40. This relationship was also significant in a multivariate analysis adjusted for severity of illness assessed by Simplified Acute Physiology Score III score, age, gender, admission diagnosis, and pre-existing comorbidities. It was not found in patients with CKD 5 on renal replacement therapy, in patients below 60 years of age, and those with diabetes mellitus requiring insulin treatment.

CONCLUSIONS

BMI is associated with better outcomes in CKD 3-5 patients who have acquired acute intermittent diseases and are admitted to an ICU, but not those requiring renal replacement therapy. This higher tolerance to acute disease processes may in part explain the "obesity paradox" observed in CKD patients.

Impact of body mass index on survival in patients undergoing peritoneal dialysis: Analysis of data from the Insan Memorial End-Stage Renal Disease Registry of Korea (1985-2014)

Background

Significant increases in the prevalence of obesity have been observed among patients with peritoneal dialysis (PD). The impact of body mass index (BMI) on survival remains unknown in Korean PD patients.

Methods

Among data of 80,674 patients on PD acquired from the Insan Memorial ESRD Registry database for the years 1985 to 2014, 6,071 cases were analyzed. Subjects were classified by baseline BMI; < 21.19 kg/m² (quartile 1, n = 1,518), 21.19 to 23.18 kg/m² (quartile 2, reference; n = 1,453), 23.19 to 25.71 kg/m² (quartile 3, n = 1,583), and > 25.71 kg/m² (quartile 4, n = 1,517).

Results

Mean age was 65.8 years, and baseline BMI was 23.57 kg/m². Numbers of male and diabetic patients were 3,492 (57.5%) and 2,192 (36.1%), respectively. Among 6,071 cases, 2,229 (36.7%) all-cause deaths occurred. As a whole, Kaplan–Meier survival curves according to BMI quartiles was significantly different (P = 0.001). All-cause mortality was significantly higher in quartile 4 than in the reference (hazard ratio [HR] = 1.154, 95% confidence interval [CI], 1.025–1.300; P = 0.018). There was no statistical difference in all-cause mortality among BMI quartiles in diabetic patients on PD. In non-diabetic patients, all-cause mortality of quartiles 1 and 3 was not different from the reference, but the HR was 1.176 times higher in quartile 4 (95% CI, 1.024–1.350; P = 0.022).

Conclusion

Baseline BMI > 25.71 kg/m² seems to be an important risk factor for all-cause mortality in Korean PD patients.

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.

The association between body mass index and mortality among Asian peritoneal dialysis patients: A meta-analysis

BACKGROUND

Previous studies have revealed that increased body mass index (BMI) is associated with decreased mortality among hemodialysis patients. However, few studies have dealt with the association between BMI and mortality among patients undergoing peritoneal dialysis (PD) and even fewer studies have focused on the Asian PD patients. The reported studies were often non-conclusive and some even yielded contradictory results. This paper, to our best knowledge, registers the first attempt to systematically review the current literature and summarize new results on the association between BMI and mortality among the Asian PD population.

METHOD

A systematic literature review was performed in Medline and EMBASE to identify relevant cohort studies on all-cause and cardiovascular disease (CVD) mortality stratified by BMI categories tailored to Asians among the Asian PD population. We meta-analyzed individual results based on a random effect model, strictly complying with Preferred Reporting Items for Systematic Reviews and Meta-analysis.

RESULTS

The paper reviews seven cohort studies with a total of 3,610 Asian PD patients. Obese group (BMI = 25-29.9 kg/m2) was associated with higher risk of all-cause mortality (HR = 1.46, 95%CI [1.07-1.98]; p = 0.02) and CVD mortality (HR = 2.01, 95%CI [1.14-3.54]; p = 0.02), compared to the normal group (BMI = 18.5-22.9 kg/m2). The underweight group (BMI<18.5kg/m2) was also associated with an elevated risk of all-cause mortality (HR = 2.11, 95%CI [1.46-3.07]; p<0.001). No significant associations between BMI with all-cause mortality were found among the overweight group (23-24.9 kg/m2) (HR = 1.00, 95%CI [0.76-1.32]; p = 0.9). The association between BMI and CVD mortality risk among the underweight and overweight groups was found nonsignificant (p = 0.5 and 0.6 respectively).

CONCLUSION

Obesity is associated with increased mortality in Asian PD patients. The study indicates a "V-shaped" trend in the association between BMI and mortality in these patients.

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.

Association of Adiponectin with High-Sensitivity C-Reactive Protein and Clinical Outcomes in Peritoneal Dialysis Patients: A 3.5-Year Follow-Up Study

Introduction

Adiponectin (ADPN), one of most abundant fat-derived biologically active substances, plays an important role in anti-atherosclerotic process. There are conflicting results about the impact of ADPN on cardiovascular (CV) outcomes and mortality, particularly in patients undergoing peritoneal dialysis (PD). Moreover, the relationship between ADPN and inflammatory mediators has been seldom explored in this population. Therefore, we examined the relationship between ADPN and longitudinal high-sensitivity C-reactive protein (hs-CRP) changes and investigated whether ADPN or hs-CRP levels could predict CV outcomes and mortality in prevalent PD patients after comprehensive adjustment of possible confounders.

Methods

In this prospective cohort study, 78 PD patients were enrolled and followed from February 2009 to August 2012. During follow-up, CV events and all-cause mortality were recorded.

Results

The mean baseline ADPN value was 29.46±18.01 μg/ml and duration of PD treatment was 37.76±36.96 months. In multiple linear regression analysis, plasma ADPN levels positively correlated with high-density lipoprotein and negatively associated with hs-CRP, body mass index, D4/D0 glucose, triglyceride, and duration of PD treatment. After stratified by genders, the inverse association between baseline ADPN and hs-CRP was more significant in the female group. The hs-CRP levels were followed up annually and remained significantly lower in the high ADPN group in the first 2 years. Patients were then stratified into two groups according to the median ADPN value (23.8 μg/ml). The results of Kaplan-Meier survival analysis demonstrated less CV events and better survival in high ADPN group. On multivariate Cox regression analysis, only ADPN level (HR: 0.93, 95% CI: 0.88–0.98, p = 0.02), age and history of CV diseases were independent risk factors for future CV events. Furthermore, hs-CRP (HR: 1.11, 95% CI:1.001–1.22, p = 0.04) was identified as independent predictor of all-cause mortality.

Conclusions

Serum hs-CRP levels were consistently lower in the high ADPN group during 2-year follow-up. We also demonstrated the importance of ADPN and hs-CRP in predicting CV events and all-cause mortality in PD population during 3.5-year follow-up.

Association of Body Mass Index With Mortality in Peritoneal Dialysis Patients: A Systematic Review and Meta-Analysis

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BACKGROUND

Although higher body mass index (BMI) is associated with better outcomes in hemodialysis patients, the relationship in peritoneal dialysis (PD) patients is less clear. We aimed to synthesize the results from all large and high-quality studies to examine whether underweight, overweight, or obesity is associated with any significantly different risk of death in peritoneal dialysis patients. ♦

METHODS

We searched MEDLINE, EMBASE, Web of Science, CINAHL, and Cochrane CENTRAL, and screened 7,123 retrieved studies for inclusion. Two investigators independently selected the studies using predefined criteria and assessed each study's quality using the Newcastle-Ottawa Quality Assessment Scale. We meta-analyzed the results of the largest studies with no overlap in their data sources. ♦

RESULTS

We included 9 studies (n = 156,562) in the systematic review and 4 studies in the meta-analyses. When examined without stratifying studies by follow-up duration, the results of the studies were inconsistent. Hence, we pooled the study results stratified based upon their follow-up durations, as suggested by a large study, and observed that being underweight was associated with higher 1-year mortality but had no significant association with 2- and 3- to 5-year mortalities. In contrast, being overweight or obese was associated with lower 1-year mortality but it had no significant association with 2-, and 3- to 5-year mortalities. ♦

CONCLUSION

Over the short-term, being underweight was associated with higher mortality and being overweight or obese was associated with lower mortality. The associations of body mass with mortality were not significant over the long-term.

The association between body mass index and mortality in incident dialysis patients

OBJECTIVES

To study the body mass index (BMI) trajectory in patients with incident end-stage kidney disease and its association with all-cause mortality.

METHODS

This longitudinal cohort study included 17022 adult patients commencing hemodialysis [HD] (n = 10860) or peritoneal dialysis [PD] (n = 6162) between 2001 and 2008 and had ≥6-month follow-up and ≥2 weight measurements, using the Australia and New Zealand Dialysis and Transplant Registry data. The association of time-varying BMI with all-cause mortality was explored using multivariate Cox regression models.

RESULTS

The median follow-up was 2.3 years. There was a non-linear change in the mean BMI (kg/m2) over time, with an initial decrease from 27.6 (95% confidence interval [CI]: 27.5, 27.7) to 26.7 (95% CI: 26.6, 26.9) at 3-month, followed by increments to 27.1 (95% CI: 27, 27.2) at 1-year and 27.2 (95% CI: 26.8, 27.1) at 3-year, and a gradual decrease subsequently. The BMI trajectory was significantly lower in HD patients who died than those who survived, although this pattern was not observed in PD patients. Compared to the reference time-varying BMI category of 25.1-28 kg/m2, the mortality risks of both HD and PD patients were greater in all categories of time-varying BMI <25 kg/m2. The mortality risks were significantly lower in all categories of time-varying BMI >28.1 kg/m2 among HD patients, but only in the category 28.1-31 kg/m2 among PD patients.

CONCLUSIONS

BMI changed over time in a non-linear fashion in incident dialysis patients. Time-varying measures of BMI were significantly associated with mortality risk in both HD and PD patients.

Body mass index and mortality risk in Asian peritoneal dialysis patients in Hong Kong-impact of diabetes and cardiovascular disease status

BACKGROUND

Obesity increases mortality in the general population, but improves survival in hemodialysis patients. In peritoneal dialysis (PD) patients, the reported effect is controversial. We investigated the effect of body mass index (BMI) on patient survival in Asian PD patients.

METHODS

The survival of incident Asian PD patients from 2001 to 2008 in a single center in Hong Kong was analyzed retrospectively. Baseline demographic and clinical data were collected from patient records. Patients who had a total Kt/V below 1.7 or who died within 6 months were excluded. The BMI was categorized using the World Health Organization recommendation for Asian populations.

RESULTS

In the 274 study patients [154 men (56%); 138 with diabetes (50.4%); mean age: 63.4 ± 14.6 years; mean BMI: 21.97 ± 3.23 kg/m(2); 37 underweight (13.5%); 35 obese (12.8%)], the relative risk (RR) for mortality [adjusted for age, diabetes status, and cardiovascular disease (CVD)] was similar for the normal and overweight groups, but higher for the underweight (RR: 1.909; p = 0.028) and obese groups (RR: 1.799; p = 0.048). The increased mortality in obese patients was more prominent in patients with diabetes (RR: 1.9 vs 1.19 in patients without diabetes; p = 0.074 and 0.76 respectively), and in patients with CVD (RR: 8.895 vs 1.642 in patients without CVD; p = 0.012 and 0.122 respectively).

CONCLUSIONS

In Asian PD patients, the relationship between BMI and mortality was U-shaped, with higher mortality in the underweight and obese patients. The negative impact of obesity was more prominent in patients with diabetes and CVD.

Body size and longitudinal body weight changes do not increase mortality in incident peritoneal dialysis patients of the Brazilian peritoneal dialysis multicenter study

OBJECTIVES

To determine the roles of body size and longitudinal body weight changes in the survival of incident peritoneal dialysis patients.

PATIENTS AND METHODS

Patients (n = 1911) older than 18 years of age recruited from 114 dialysis centers (Dec/ 2004-Oct/2007) and participating in the Brazilian Peritoneal Dialysis Multicenter Cohort Study were included. Clinical and laboratory data were collected monthly (except if the patient received a transplant, recovered renal function, was transferred to hemodialysis, or died).

RESULTS

Survival analyses were performed using Kaplan-Meier survival curves and Cox proportional hazards. Total follow-up was 34 months. The mean age was 59 years (54% female). The weight category percentages were as follows: underweight: 8%; normal: 51%; overweight: 29%; and obese 12%. The multivariate model showed a higher risk of death for a body mass index <18.5 kg/m², a neutral risk between 25 and 29.9 kg/m² and a protective effect for an index >30 kg/m². Patients were divided into five categories according to quintiles of body weight changes during the first year of dialysis: <-3.1%, -3.1 to+0.12%, +0.12 to <+3.1% (reference category), +3.1 to +7.1% and >+7.1%. Patients in the lowest quintile had significantly higher mortality, whereas no negative impact was observed in the other quintiles.

CONCLUSION

These findings suggest that overweight/obesity and a positive body weight variation during the first year of peritoneal dialysis therapy do not increase mortality in incident dialysis patients in Brazil.

Waist-to-Hip Ratio, Cardiovascular Outcomes, and Death in Peritoneal Dialysis Patients

Objectives. The primary objective of this study was to determine the relationship between waist-to-hip ratio (WHR), cardiovascular (CV) events, and mortality in peritoneal dialysis (PD) patients. A secondary objective was to investigate the association between abdominal obesity and systemic inflammatory markers. Methods. This is a prospective study of 22 prevalent PD patients. WHR was measured at baseline. C-reactive protein (CRP), tumour necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were measured. Main outcomes were first CV event and death from all causes. Survival analysis was used to examine the relationship between anthropomorphic measures and clinical outcomes. Results. Mean follow-up period was 3.1 years. In Kaplan-Meier analysis, survival was lower in those with higher WHR (P = .002). In Cox regression, WHR independently predicted mortality and first CV event after adjustment for known ischemic heart disease (hazard ratio [HR] 1.17, confidence interval [CI] 1.05-1.30 for death; HR 1.13, CI 1.01-1.26 for CV event). WHR correlated with serum TNF-α (r = 0.45; P = .05). Conclusion. The results of this study suggest WHR may be a risk factor for increased CV events and mortality in PD patients. Abdominal obesity is also associated with inflammatory markers. Larger studies are warranted to confirm these findings.

Body mass index and risk of all-cause and cardiovascular mortality in hospitalized elderly patients with diabetes mellitus

AIMS

Obesity is linked to increased morbidity and mortality risk in both the general population and in patients with diabetes mellitus; however, recent reports suggest that, in hospitalized elderly individuals, the association between body mass index (BMI) and mortality may be inverse. The present study sought to investigate the association between BMI and survival in hospitalized elderly individuals with diabetes mellitus.

METHODS

The medical records of 470 patients (226 males, mean age of 81.5 +/- 7.0 years) admitted to an acute geriatric ward between 1999 and 2000 were reviewed. Of the 140 patients with diabetes mellitus, 122 had more than 6 months of follow-up and were included in this analysis. Patients were followed up until 31 August 2004. Mortality data were extracted from death certificates.

RESULTS

During a mean follow-up of 3.7 +/- 1.6 years, 69 (56.6%) subjects died, 31 (25.4%) from cardiovascular causes. Those who died from any cause had lower baseline BMI than those who survived (24.0 +/- 4.0 vs. 27.1 +/- 4.3 kg/m(2); P < 0.0001). Similarly, those who died of cardiovascular causes had lower baseline BMI than those who did not (23.7 +/- 3.6 vs. 25.9 +/- 4.5, P = 0.01). BMI was inversely associated with all-cause [relative risk (RR) 0.89, 95% confidence interval (CI) 0.83-0.96, P = 0.002] and cardiovascular death (RR 0.83, 95% CI 0.74-0.93, P = 0.002) even after controlling for age, sex, smoking, dyslipidaemia and reason for hospital admission.

CONCLUSIONS

In very elderly subjects with diabetes mellitus, increased BMI was associated with reduced mortality risk.