Obesity and the epidemiology and prevention of kidney disease: waist circumference versus body mass index

Central obesity and risks of cardiovascular events and mortality in prevalent hemodialysis patients

BACKGROUND

To date, no attempt has been made to assess the best anthropometric method for defining abdominal adiposity in hemodialysis (HD) patients or to determine whether the quantity of intra-abdominal fat relates to morbidity and mortality in that population. We aimed to describe the prevalence of central obesity in HD patients and to investigate the relationship between central obesity assessed by anthropometric variables, and composite outcomes, cardiovascular morbidity and mortality among HD patients and whether this parameter correlates with intra-abdominal fat assessed by computed tomography scan (CT scan).

METHODS

The procedures followed were in accord with the ethical standards of the committee on human experimentation of our institution. Informed oral consent was obtained from all patients. This was a cross-sectional study of 120 prevalent HD patients. Anthropometric measurements including body mass index, conicity index (Ci), waist-hip ratio (WHR), waist circumference (WC), waist-to-height ratio (WHtR), and visceral adiposity index (VAI) were recorded. Visceral and subcutaneous abdominal fat were assessed by CT scan. Comorbidity was scored for both the Charlson comorbidity index (CCI) and Davies comorbidity index.

RESULTS

Twenty-eight patients (23.3%) were centrally obese based on anthropometry. By linear regression analysis, Ci, WHR, and VAI were predictors of CT assessed central obesity; p 0.042, 0.001, and 0.010, respectively. On assessment of the relationship between the abdominal obesity and the comorbidity indices, there was a positive significant correlation between Ci and CCI (p 0.025) and Davies score (p 0.002) which are predictors of mortality. During the mean follow-up period (3.2 years), 56 patients reached the composite outcome; eight patients died and 48 experienced CV events. Central obesity measured by anthropometry was a predictor of composite outcomes, cardiovascular morbidity, and mortality in HD patients by regression analysis and cox regression model. Only WC and WHtR did not predict mortality.

CONCLUSION

Ci, WHR, and VAI are cheap alternatives for accurate assessment of morbidity and mortality risk in centrally obese prevalent HD patients.

Deleterious Effects of Increased Intra-Abdominal Pressure on Kidney Function

Elevated intra-abdominal pressure (IAP) occurs in many clinical settings, including sepsis, severe acute pancreatitis, acute decompensated heart failure, hepatorenal syndrome, resuscitation with large volume, mechanical ventilation with high intrathoracic pressure, major burns, and acidosis. Although increased IAP affects several vital organs, the kidney is very susceptible to the adverse effects of elevated IAP. Kidney dysfunction is among the earliest physiological consequences of increased IAP. In the last two decades, laparoscopic surgery is rapidly replacing the open approach in many areas of surgery. Although it is superior at many aspects, laparoscopic surgery involves elevation of IAP, due to abdominal insufflation with carbonic dioxide (pneumoperitoneum). The latter has been shown to cause several deleterious effects where the most recognized one is impairment of kidney function as expressed by oliguria and reduced glomerular filtration rate (GFR) and renal blood flow (RBF). Despite much research in this field, the systemic physiologic consequences of elevated IAP of various etiologies and the mechanisms underlying its adverse effects on kidney excretory function and renal hemodynamics are not fully understood. The current review summarizes the reported adverse renal effects of increased IAP in edematous clinical settings and during laparoscopic surgery. In addition, it provides new insights into potential mechanisms underlying this phenomenon and therapeutic approaches to encounter renal complications of elevated IAP.

Longitudinal association of body mass index and waist circumference with left ventricular mass in hypertensive predialysis chronic kidney disease patients

Background

This study aimed to investigate the association of both body mass index (BMI) and waist circumference (WC) with left ventricular mass (LVM) in hypertensive predialysis chronic kidney disease (CKD) patients.

Methods

From 2004 to 2005, 206 consecutive incident adult patients from the outpatient CKD clinics of two hospitals in Greece were included. Inclusion criteria were the presence of CKD and hypertension. BMI (kg/m²), WC (cm) and LVM (g) were assessed annually for 3 years.

Results

The mean age was 68.1 years, mean BMI 29.1 kg/m² and mean WC was 103.7 cm. The median LVM was 245.7 g (n = 179). In the cross-sectional data, linear regression models showed that WC {β = 1.2 [95% confidence interval (CI) 0.15; 2.3]}, and not BMI [β = 2.1 (95% CI: −0.70; 4.8)], was significantly associated with LVM. After adjustment for age, sex, primary renal disease, smoking and history of cardiovascular disease, both BMI [β = 4.7 (95% CI: 2.0; 7.4] and WC [β = 1.2 (95% CI: 0.14; 2.3)] were significantly associated with LVM. These associations were pronounced in CKD stage 1–3, but not in CKD stage 4–5. In the longitudinal analysis, linear mixed models adjusting for confounders showed that both an increase in BMI [β = 2.9 (95% CI: 0.74; 5.1)] and an increase in WC [β = 1.1 (95% CI: 0.28; 1.8)] were significantly associated with an increase in LVM.

Conclusions

In hypertensive predialysis CKD patients, both BMI and WC were associated with LVM in CKD stage 1–3, but not in CKD stage 4–5. In the longitudinal analysis, both an increase in BMI and WC were associated with an increase in LVM. Future studies should focus on mechanisms responsible for the associations between anthropometric variables and LVM.

Visceral fat and coronary artery calcification in patients with chronic kidney disease

BACKGROUND

Abdominal fat is a metabolically active tissue which has been associated with cardiovascular events and death in chronic kidney disease (CKD) patients. We explore here the association between surrogates of abdominal fat and coronary artery calcium score (CACs).

METHODS

Cross-sectional analysis of 232 non-dialysis-dependent CKD patients Stages 3-5 (median age 60 [25th-75th percentile 52-67] years; 60% men). Visceral adipose tissue (VAT) and CACs were assessed by computed tomography. Surrogates of abdominal fat included VAT and waist circumference (WC).

RESULTS

VAT was positively associated with CACs in univariate analysis (ρ = 0.23). Across increasing VAT quartiles, patients were older, more often men and smokers. Although increasing VAT quartiles associated with higher glomerular filtration rate and leptin, better nutritional status (subjective global assessment) as well as larger muscle stores and strength, they were also more insulin resistant (HOMA-IR), dyslipidemic and inflamed (C-reactive protein and white blood cells). In addition, CACs were incrementally higher. Clinically evident coronary artery calcification (CACs ≥ 10 Agatston) was present in 63% of the patients. Both increased visceral fat (odd ratio 1.60 [95% CI 1.23-2.09] per standard deviation increase) and increased WC (1.05 [1.01-1.12] per cm increase), augmented the odds to present calcification. Such associations remained statistically significant after extensive multivariate adjustment for confounders.

CONCLUSIONS

Abdominal fat is associated with coronary artery calcification in non-dialysis dependent CKD patients, supporting its potential role as a cardiovascular risk factor in uremia.

Assessment of obesity in chronic kidney disease: what is the best measure?

PURPOSE OF REVIEW

Obesity is a major driver of the current epidemic of chronic kidney disease (CKD), but metrics of obesity in the CKD population have been studied sparsely. This review updates knowledge on this issue.

RECENT FINDINGS

Measures of abdominal obesity, waist circumference and waist-to-hip ratio (WHR), are better predictors than BMI of the high risk of mortality in predialysis and dialysis patients and waist circumference reliably reflects visceral fat in CKD patients. Skinfold thickness and WHR are superior to BMI for the classification of obesity in CKD patients. Multifrequency body impedance analysis (BIA) provides valid estimates of fat mass in hemodialysis patients.

SUMMARY

Skinfold thickness,WHR and multifrequency BIA are superior to BMI for measuring body fat in CKD patients and measures of abdominal obesity are stronger predictors of adverse clinical outcomes than the BMI. These metrics should be preferentially applied for the assessment of obesity in CKD, but it remains unproven that these techniques offer real advantages over the BMI in clinical practice in CKD patients.

Trends in estimated kidney function: the FINRISK surveys

We evaluated the temporary trend in estimated glomerular filtration rate (eGFR) of subjects aged from 25 to 74 years between two cross-sectional population surveys in 2002 and in 2007. The mean eGFR across age-groups, the prevalences of eGFR categories, and the prevalence of chronic kidney disease (CKD) stage 3–5 defined by eGFR\60 mL/min/1.73 m2 were defined in sex- and age-specific groups using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) Study equation. The eGFR decreased from year 2002 to 2007 across the age-groups in both genders. The prevalence of CKD stage 3–5 (eGFR\60 mL/min/1.73) increased in women from 1.8 to 3.1% (P=0.017), but not in men. In the combined analysis of both genders, CKD stage 3–5 was markedly more common in 2007 compared to 2002, with odds ratio (OR) 1.59 (95% confidence interval (CI) 1.22–2.08) remaining significant after adjusting the model for age, gender, study area, hypertension, obesity, prior cardiovascular disease, and diabetes mellitus, and being at lowest when only age, gender and waist circumference were included in the model (OR 1.34; 95% CI 1.02–1.76). To conclude, the mean eGFR decreased significantly during 2002–2007 in both sexes, and CKD stage 3–5 increased in women. This trend was concurrent with increases in mean waist circumference and in the prevalence of diabetes mellitus.

Extraglomerular C3 deposition and metabolic impacts in patients with IgA nephropathy

BACKGROUND

The aim of the present study was to explore the significance of extraglomerular (Bowman's capsule and/or arteriole) C3 (ex-C3) deposits in IgA nephropathy (IgAN).

METHODS

One hundred and seventy patients with IgAN were divided into two groups: Group A (n=79), patients who did not have ex-C3 deposits, and Group B (n=91), patients who had ex-C3 deposits.

RESULTS

At the time of renal biopsy, Group B was characterized by a marked increase in diastolic blood pressure, total cholesterol, triglyceride and low-density lipoprotein-cholesterol compared with those of Group A. After 4 years, the estimated glomerular filtration rate (eGFR) in Group B was significantly worse than that of Group A. Upon examination by electron microscopy, the arteriolar dense deposits in Group B were found to occur in significantly higher amounts than in Group A. One hundred and thirty-four patients underwent a 3-year follow-up study after intervention and were re-divided by therapeutic factors as follows: 'conventional therapy', treatment with anti-hypertensive drugs and/or anti-platelet drugs, and 'aggressive therapy', additional treatment with either tonsillectomy or corticosteroid. Patients treated with conventional therapy in Group B had significantly higher body mass index and levels of C3 and CH50 compared with other Groups. Aggressive therapy was significantly effective in urinary protein reduction in both Group A and Group B. Except for the patients who received aggressive therapy in Group A, the levels of the eGFR gradually declined.

CONCLUSIONS

It appears that IgAN patients who have ex-C3 deposits have worse clinical outcomes.

Differential effect of baseline adiponectin on all-cause mortality in hemodialysis patients depending on initial body mass index. Long-term follow-up data of 4.5 years

OBJECTIVES

We sought to investigate the interaction of adiponectin levels and body mass index (BMI) for predicting all-cause mortality in a cohort of hemodialysis (HD) patients.

DESIGN

Longitudinal, observational cohort study.

SETTING

HD unit.

SUBJECTS

Sixty patients (mean age: 64 ± 13 years, 39 men) with end-stage renal disease on maintenance HD followed up for 4.5 years represented the prospective study cohort.

INTERVENTION

Associations between baseline plasma adiponectin levels and initial BMI with all-cause mortality were assessed taking into account the assumption of nonlinear correlations. The association between adiponectin, BMI, and serum levels of interleukin-10 (IL-10) and interleukin-6 (IL-6) with survival was determined cross-sectionally.

MAIN OUTCOME MEASURE

All-cause mortality.

RESULTS

Nonlinear survival modeling showed that there was a U-shaped association of BMI with all-cause mortality, whereas there was an inverse U-shaped association for plasma adiponectin levels. Using a BMI of 24 kg/m(2) as a cutoff, an interaction effect of BMI on the association between adiponectin and mortality was observed (P = .045). In participants with BMI ≥ 24 kg/m(2), each 15 μg/mL increase in plasma adiponectin levels was associated with a decreased hazard of death (hazard ratio: 0.57, 95% CI: 0.32 to 0.99) in unadjusted analysis. In HD patients with BMI < 24 kg/m(2), no significant association was observed between adiponectin and mortality (P = .989). Cross-sectional analysis showed that in the subgroup of patients in whom the protective effect of adiponectin was observed (BMI ≥ 24 kg/m(2)), a positive linear association existed between adiponectin and IL-10 levels (r = 0.345, P = .027) as well as a negative association with IL-6 levels (r = -0.322, P = .040). No association was observed in patients with BMI < 24 kg/m(2), neither with IL-10 nor with IL-6.

CONCLUSIONS

Obesity possibly modifies the effect of adiponectin on all-cause mortality in HD patients, thus explaining the published conflicting results in recent literature regarding the association of plasma adiponectin levels and mortality in chronic kidney disease patients.

Overweight, obesity and intentional weight loss in chronic kidney disease: NHANES 1999-2006

Objective

Obesity and chronic kidney disease (CKD) have emerged as major public health problems. We aimed to examine: a) lifestyle and behavioral factors, b) factors related to pursuing weight loss, and c) weight loss modalities pursued by CKD and non-CKD individuals who are overweight and obese.

Methods

Cross-sectional analysis of 10,971 overweight and obese adult participants in the National Health and Nutrition Examination Surveys conducted between 1999-2006. We examined the differences in lifestyle and behavioral factors between CKD and non-CKD participants and factors associated with pursuing weight loss using survey regression models.

Results

The total daily energy intake of the CKD population was lower than the non-CKD group (1987 kcal/day vs. 2063 kcal/day, p=0.02) even after adjusting for relevant covariates. However, the percentage of energy derived from protein was similar between the groups. Sixty-six percent of the CKD population did not meet the minimum recommended leisure time physical activity goals compared to 57% among non-CKD (p<0.001). Fifty percent of CKD participants pursued weight loss (vs. 55% of non-CKD individuals, p=0.01), but the presence of CKD was not independently associated with the pursuit of weight loss in the multivariate model. Among participants pursuing weight loss, modalities including dietary interventions utilized by CKD and non-CKD participants were similar. Eight percent of CKD participants used medications to promote weight loss.

Conclusions

Among the overweight and obese population, lifestyle and behavioral factors related to obesity and weight loss are similar between CKD and non-CKD participants. Insufficient data exist on the beneficial effects of intentional weight loss in CKD and these data show that a significant proportion of the CKD population use diets that may have high protein content and medications to promote weight loss that may be harmful. Future clinical trials evaluating the efficacy and optimal modalities to treat obesity in the CKD population are warranted.