Obesity, Cardiovascular and All-Cause Mortaliy in Chronic Kidney Disease - A Systematic Review and Meta-Analysis.

Abstract

Background: The role of obesity as a risk factor for premature cardiovascular disease and death in people with chronic kidney disease (CKD) is uncertain due to inconsistent findings across the spectrum of CKD, and among published studies. Aim: Our study aimed to determine the association between obesity measured by body mass index (BMI), waist to hip ratio (WHR) and waist circumference (WC) and risk of death, cardiovascular mortality, and non-fatal cardiovascular events in people with CKD, stratified by stage, and to compare the prognostic strength of the various measures of obesity. Methods: MEDLINE and Embase were searched without language restriction through to May 2013. Hand searches were also conducted. Data were summarised using random effects models where possible. Results: Of the 3413 citations identified, a total of 94 cohorts (n=859,842 participants) assessed the association of one or more measures of obesity and all-cause and cause-specific mortality or cardiovascular outcome in patients with CKD. For every 1 kg/m2 increase in BMI, there was a 3% reduction in all-cause mortality and 4% reduction in cardiovascular mortality in CKD-dialysis (HR 0.97; 95%CI 0.96-0.98 and HR 0.96; 95%CI 0.92-1.00 respectively). In CKD-predialysis, for every 1 kg/m2 increase in BMI there was a 2% reduction in all-cause mortality (HR 0.98; 95%CI 0.0.96-1.00). There were no significant relationship between BMI and mortality in transplanted patients (HR 1.01 95%CI 0.97-1.05). Five cohort studies in total assessed the association between WHR, WC and all-cause mortality but no robust conclusions could be made. Incomplete reporting of prognostic factor and outcome measurement assessment were major limitations of the available studies. Conclusion and Relevance: Pre-dialysis and dialysis patients with a low BMI are at higher risk of mortality and cardiovascular mortality. BMI is not associated with post-transplant mortality. Higher BMI in potential recipients should therefore not preclude this group from consideration for transplantation. Further research is needed to determine if the lack of association between BMI and outcomes in transplanted patients is related to BMI being a poor measure of obesity.