Supplementary Material for: The Association of Serum Iron with Congestive Heart Failure: Evidence from a Cross-Sectional Analysis of NHANES 2017–2020

Abstract
Introduction: Heart failure (HF) is a major global health concern with complex pathophysiological mechanisms. Iron, a crucial micronutrient for cardiac function, has been increasingly researched for its potential link with HF. This study aims to investigate the association between serum iron levels and congestive heart failure (CHF) using cross-sectional data from the NHANES database (2017-2020), thereby contributing to the understanding and management of HF.
Methods: This cross-sectional analysis utilized data from the National Health and Nutrition Examination Survey (NHANES), focusing on American adults. CHF status was identified through self-reported medical history. Serum iron levels were measured using the Roche Cobas 6000 analyzer. Covariates included demographics, lifestyle factors, and comorbidities. Statistical analyses involved logistic regression models, adjusting for potential confounders to evaluate the association between serum iron and CHF.
Results: Among 7,298 participants (240 with CHF and 7,058 without CHF), those with CHF had significantly lower serum iron levels. Higher serum iron levels were associated with a reduced incidence of CHF, even after adjusting for covariates. Subgroup analyses revealed this association to be particularly significant in older adults, hypertensive, diabetic, smokers, obese, and those with renal impairment. The optimal serum iron cutoff value for CHF risk was identified as 15.1μmol/L.
Conclusion: This study demonstrates a negative association between serum iron levels and CHF occurrence, suggesting serum iron as a potential marker for CHF diagnosis and management.