Despite obese patients having lower NT-proBNP levels, the peptide biomarker still reliably predicted 180-day mortality in acute heart failure regardless of body weight.
p=0.24No significant interaction between BMI and NT-proBNP for predicting 180-day mortality — the test works across all weight classes
What the researchers found
Although obese patients with acute heart failure had lower NT-proBNP levels than non-obese patients (inverse correlation, p<0.001 across BMI classes), the peptide biomarker's ability to predict death at 180 days was not affected by obesity. NT-proBNP remained a reliable prognostic indicator for long-term mortality regardless of BMI class, with no significant interaction between BMI and NT-proBNP for 180-day mortality (interaction p=0.24).
However, for the combined endpoint of 30-day death or heart failure rehospitalization, there was a significant BMI-NT-proBNP interaction (p=0.02), suggesting the relationship between NT-proBNP and short-term outcomes may differ by weight category.
Why it matters
Doctors have worried that NT-proBNP blood tests are less useful in obese heart failure patients because obesity lowers natriuretic peptide levels, potentially masking disease severity. This study provides reassurance: even though obese patients have lower baseline levels, NT-proBNP still accurately predicts who is most likely to die within six months. This is clinically crucial because obesity and heart failure frequently coexist.
The numbers in context
n=686 · Median age 67 years · 71% female · NT-proBNP inversely correlated with BMI (p<0.001) · No BMI×NT-proBNP interaction for 180-day mortality (p=0.24) · Significant interaction for 30-day death/rehospitalization (p=0.02) · 4 BMI classes analyzed
How the study worked
This was a secondary analysis of 686 patients from the biomarker substudy of ASCEND-HF, a randomized clinical trial of nesiritide in acute decompensated heart failure. Patients were classified into four WHO obesity categories (non-obese, Class I, II, and III). Researchers measured NT-proBNP at baseline and assessed the interaction between BMI class and NT-proBNP levels for predicting 30-day and 180-day outcomes including death and heart failure rehospitalization.
Who was studied
686 patients with acute decompensated heart failure from the ASCEND-HF trial biomarker substudy, median age 67, 71% female, across all BMI classes
What this study cannot tell us
This is a substudy of a larger trial, so the 686-patient sample was not specifically powered for this analysis. The predominance of female participants (71%) may limit generalizability. The study examined only baseline NT-proBNP, not serial measurements. The significant interaction found for the 30-day composite endpoint but not 180-day mortality suggests the relationship may be more complex than a simple yes/no answer.
How to read the evidence
This is a well-designed substudy from a major randomized clinical trial (ASCEND-HF) published in JAHA. The sample of 686 patients with documented NT-proBNP levels and rigorous outcome tracking provides moderate-high evidence, though it was not primarily powered for this specific analysis.
When this study was published
Published in 2018, this analysis from the ASCEND-HF trial remains relevant as the obesity-natriuretic peptide relationship continues to be debated in cardiology. The findings align with subsequent studies supporting NT-proBNP's utility in obese populations.
The bigger picture
The so-called 'obesity paradox' in natriuretic peptide testing has concerned cardiologists for years — obese patients have lower BNP/NT-proBNP levels, which could theoretically lead to underdiagnosis or underestimation of severity. This ASCEND-HF substudy adds to growing evidence that while absolute levels are lower, the prognostic utility of these peptide biomarkers is preserved. This has implications for clinical guidelines and diagnostic cut-off thresholds.
Questions still open
- Should NT-proBNP diagnostic cut-offs be adjusted for BMI, even if the prognostic value is preserved?
- Why does the BMI-NT-proBNP interaction appear significant at 30 days but not 180 days — does body composition affect short-term vs long-term prognosis differently?
- Would serial NT-proBNP measurements (rather than just baseline) show different BMI interactions in obese heart failure patients?
Common questions
Why do obese people have lower NT-proBNP levels?
Should doctors use different NT-proBNP thresholds for obese patients?
Read the original research
Interaction of Body Mass Index on the Association Between N-Terminal-Pro-b-Type Natriuretic Peptide and Morbidity and Mortality in Patients With Acute Heart Failure: Findings From ASCEND-HF (Acute Study of Clinical Effectiveness of Nesiritide in Decompensated Heart Failure).
Journal of the American Heart Association, 7(3)
Citation
Bhatt, Ankeet S; Cooper, Lauren B; Ambrosy, Andrew P; Clare, Robert M; Coles, Adrian; Joyce, Emer; Krishnamoorthy, Arun; Butler, Javed; Felker, G Michael; Ezekowitz, Justin A; Armstrong, Paul W; Hernandez, Adrian F; O'Connor, Christopher M; Mentz, Robert J. (2018). Interaction of Body Mass Index on the Association Between N-Terminal-Pro-b-Type Natriuretic Peptide and Morbidity and Mortality in Patients With Acute Heart Failure: Findings From ASCEND-HF (Acute Study of Clinical Effectiveness of Nesiritide in Decompensated Heart Failure).. Journal of the American Heart Association, 7(3). https://doi.org/10.1161/JAHA.117.006740