Response to Body Mass Index-Mortality Paradox in Hemodialysis: Can It Be Explained by Blood Pressure?
Ferreira-Filho et al1 correctly point out the importance of residual renal function in maintaining volume homeostasis and predicting morbid and mortal outcomes among patients with end-stage renal disease. Although we did not report residual renal function, the vintage stratified by body mass index categories of obesity in these patients was reported. The vintage (or the dialysis age of a patient) is an important determinant of residual renal function. Few patients make urine after a few years on hemodialysis, and, therefore, they have little residual renal function. We reported that the vintage and obesity categories were not correlated statistically. However, we found that the vintage was directly related to all-cause mortality. Given the observational nature of the study, whether this association was causally related to lesser residual renal function or progressive cardiovascular disease is open to speculation. However, even after accounting for dialysis vintage (a proxy of residual renal function), there was a time-dependent relationship between the body mass index and mortality. Thus, residual renal function may not be the sole explanation for the paradox.
Indiana University School of Medicine
Richard L. Roudebush Veterans Administration Medical Center
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