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.

摘要
引言：心力衰竭（Heart Failure, HF）是全球范围内的重大公共卫生问题，其病理生理机制复杂。铁作为维持心脏功能所必需的关键微量营养素，与心力衰竭的潜在关联已受到越来越多的研究关注。本研究借助美国国家健康与营养调查（National Health and Nutrition Examination Survey, NHANES）2017-2020年的横断面数据，探讨血清铁水平与充血性心力衰竭（Congestive Heart Failure, CHF）的关联，以期为心力衰竭的认知与临床管理提供理论依据。
方法：本横断面分析采用美国国家健康与营养调查（NHANES）的数据，研究对象为美国成年人群。充血性心力衰竭（CHF）状态通过受试者自述的既往病史进行判定。血清铁水平采用罗氏Cobas 6000分析仪（Roche Cobas 6000 analyzer）进行检测。协变量涵盖人口学特征、生活方式因素及合并症情况。统计分析采用逻辑回归模型，通过校正潜在混杂因素，评估血清铁水平与CHF的关联强度。
结果：本研究共纳入7298名参与者，其中240名确诊充血性心力衰竭，7058名未患CHF。相较于非CHF人群，CHF患者的血清铁水平显著更低。在校正协变量后，更高的血清铁水平仍与CHF发病风险降低显著相关。亚组分析显示，该负相关关联在老年人、高血压患者、糖尿病患者、吸烟者、肥胖人群及肾功能受损人群中尤为显著。本研究确定的CHF风险最优血清铁截断值为15.1μmol/L。
结论：本研究证实血清铁水平与CHF发生呈负相关，提示血清铁可作为CHF诊断与临床管理的潜在生物标志物。