Received on December 11, 2006
Accepted on August 17, 2007

Endocrinology and Metabolism

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

¹ Department of Cardiology and Endocrinology, Clinic E, Frederiksberg University Hospital, Frederiksberg, Denmark
² Department of Cardiology, The Heart Centre, Rigshospitalet University Hospital, Copenhagen, Denmark
³ Department of Clinical Physiology and Nuclear Medicine, The PET Centre, Rigshospitalet University Hospital, Copenhagen, Denmark, and Cluster for Molecular Imaging, University of Copenhagen, Copenhagen, Denmark
⁴ Department of Cardiology, Roskilde University Hospital, Roskilde, Denmark

^* To whom correspondence should be addressed. E-mail: m.schou{at}dadlnet.dk.

Background: 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.

Methods: 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.

Results: 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. After adjustment for GFR, estimated by the 4-component Modification of Diet in Renal Disease formula (eGFR_MDRD), in another model 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.

Conclusions: 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.