Objective: To explore the relationship between the different body mass index (BMI) ranges and all cause mortality in hemodialysis (HD) patients.
Methods: Eligible studies assessing the effects of BMI ranges on all-cause mortality (published from 1966 to 2012) were searched, using "hemodialysis/haemodialysis" and "obese/body mass index/overweight" and "mortality/survival/reverse epidemiology/obesity paradox" in PubMed, Embase, ScienceDirect, Wilcy, Scopus and Ovid. Inclusion criteria were that trials reported mortality in HD patients according to the traditional WHO/NIH BMI classification, and BMI levels were acceptable within 2 kg/m(2). The quality of the trials was evaluated using the assessing risk of bias in studies included in Cochrane reviews. The mortality rate in HD patients was the primary endpoint of the study.
Results: With no significant heterogeneity (I(2) = 0%, P = 0.45), a fixed-effects model was used for analysis. Four studies with a total of 81 423 patients met final inclusion criteria. Compared to individuals with non-elevated BMI levels, the elevated group (BMI ≥ 25 kg/m(2)) was associated with lower all-cause mortality (OR 0.67, 95%CI 0.65 - 0.68). In a risk-adjusted sensitivity analysis, elevated BMI levels remained protective against mortality (adjusted HR 0.94, 95%CI 0.92 - 0.96).
Conclusions: High BMI levels are associated with lower all-cause mortality rate in HD patients. More stable hemodynamic status, cytokine and neurohormonal alternations, and nutritional status maybe contribute to the protective effects of BMI on the mortality of HD patients. There is a need for more prospective studies to elucidate underlying mechanisms.