Body mass index and prognosis in heart failure: differential effects according to ejection fraction phenotype

Background

The prognostic relevance of body mass index (BMI) in heart failure remains controversial, with reports of an "obesity paradox". (1) Whether this association differs according to left ventricular ejection fraction (LVEF) phenotype and persists after adjustment for clinical severity and comorbidities is not well established.

Purpose

To evaluate the association between BMI categories and 12-month clinical outcomes in heart failure, overall and stratified by LVEF phenotype.

Methods

We analysed patients enrolled in the Colombian Heart Failure Registry (RECOLFACA). BMI was classified at baseline as underweight, normal weight, overweight, or obesity. The primary outcome was a composite of all-cause mortality or heart failure hospitalisation at 12 months. Secondary outcomes included all-cause mortality and heart failure hospitalisation analysed separately. Outcomes were compared across BMI categories using χ² tests and Kaplan–Meier survival analysis. Multivariable Cox proportional hazards models adjusted for age, sex, LVEF, New York Heart Association (NYHA) functional class, diabetes mellitus, arterial hypertension, treatment and chronic kidney disease. Analyses were stratified by LVEF ≤40% and LVEF >40%.

Results

A total of 2,455 patients were included; 1,657 (67.5%) had LVEF ≤40% and 798 (32.5%) had LVEF >40%.

In the overall cohort, the incidence of the composite outcome differed across BMI categories, showing a non-significant trend (χ²=7.12, p=0.068), with underweight patients presenting the highest event rate (27.5%).

All-cause mortality varied significantly according to BMI (χ²=21.04, p<0.001), decreasing progressively from underweight (17.6%) to normal weight (11.5%), overweight (8.2%) and obesity (7.6%). Heart failure hospitalisation did not differ significantly across BMI categories (p=0.115).

In patients with LVEF ≤40%, BMI was not associated with mortality at 12 months (log-rank p=0.15). In contrast, among patients with LVEF >40%, survival differed significantly across BMI categories (log-rank p=0.0045). In multivariable analysis restricted to this group, overweight and obesity were independently associated with a lower risk of death compared with underweight status. (figure)

Conclusions

The prognostic impact of BMI in heart failure is strongly dependent on LVEF phenotype. Underweight status identifies a high-risk subgroup among patients with preserved or mildly reduced ejection fraction, whereas BMI does not independently influence outcomes in reduced ejection fraction.Figure. Mortality across BMI categoryFor image description, please refer to the figure legend and surrounding text.