Effects of Body Mass Index and Age on N-Terminal Pro–Brain Natriuretic Peptide Are Associated with Glomerular Filtration Rate in Chronic Heart Failure Patients

Abstract

Obesity is a state characterized by glomerular hyperfiltration and age-related decreases in glomerular filtration rate (GFR). Body mass index (BMI), age, and GFR are associated with plasma concentrations of N-terminal pro-brain natriuretic peptide (NT-proBNP) in chronic heart failure (CHF) patients. We hypothesized that the effects of BMI and age on plasma concentrations of NT-proBNP are associated with GFR. We obtained clinical data and laboratory test results from 345 CHF patients at the baseline visit in our heart failure clinic and examined the hypothesis using multiple linear regression models. Age (P = 0.0184), BMI (P = 0.0098), hemoglobin (P = 0.0043), heart rhythm (P <0.0001), and left ventricular ejection fraction (P <0.0001) were associated with log(NT-proBNP). After adjustment for GFR estimated by the Cockcroft and Gault equation, the parameter estimates for BMI (P = 0.3807) and age (P = 0.7238) changed markedly and became insignificant. In another model, after adjustment for GFR estimated by the 4-component Modification of Diet in Renal Disease formula (eGFR(MDRD)), the parameter estimates for age (P = 0.0674) changed markedly and became insignificant, but BMI (P = 0.0067) remained significant and unchanged. The eGFR(MDRD) is adjusted for body surface area, which may explain the difference. In CHF patients, the effect of age on NT-proBNP is associated with estimates for GFR derived from serum creatinine, and the significance of the effects of BMI on NT-proBNP depends on the method by which GFR is estimated.