Protein-energy wasting and inflammation affect the association between body mass index and mortality in Japanese hemodialysis patients

Higher body mass index (BMI) values have been reported to be associated with a lower risk of mortality in hemodialysis patients, which is referred to as reverse epidemiology. However, concomitant malnutrition and inflammation might have confounding effects on this relationship. In this study, we aimed to clarify whether the relationship between BMI and mortality in Japanese hemodialysis patients is affected by malnutrition or inflammation. We examined the risk of mortality according to BMI in 259 hemodialysis patients and also in the 167 patients who were free from malnutrition and inflammation. Among all 259 subjects, a BMI of ≥25.0 kg/m2 was not found to be associated with a decreased risk of mortality (using a BMI of 22.0 to 25.0 kg/m2 as a reference). Among the 167 patients who were free from malnutrition and inflammation, the risk of mortality was significantly increased by a BMI of ≥25.0 kg/m2 (hazard ratio: 7.85 [1.77-56.27]). Thus, reverse epidemiology was not observed among these Japanese hemodialysis patients, and being obese was only found to be a risk factor for mortality among the Japanese hemodialysis patients who were free from malnutrition and inflammation. This suggests that the influence of obesity on the risk of mortality is affected by race and/or malnutrition and inflammation. Future studies are required to clarify the mechanism responsible for mortality in obese hemodialysis patients and to identify appropriate nutritional interventions for such patients.