Associations Between Hemoglobin and Serum Iron Levels and the Risk of Mortality Among Patients with Coronary Artery Disease

Abstract

Background: This study aimed to investigate the relationship between hemoglobin and serum iron levels and mortality risk in patients with coronary artery disease (CAD).

Methods: We analyzed data from 3224 patients with CAD using Cox proportional hazards regression models to assess the association of hemoglobin and serum iron levels with cardiovascular and all-cause mortality from the Guangdong coronary artery disease cohort.

Results: Over a median follow-up period of 8.9 years, 636 patients died, including 403 from cardiovascular causes. Higher hemoglobin and serum iron levels were linked to a reduced risk of cardiovascular and all-cause mortality. Patients in the highest quartiles of hemoglobin and serum iron levels had multivariable-adjusted hazard ratios (HRs) of 0.62 (95% CI, 0.46-0.85) and 0.51 (95% CI, 0.37-0.69) for cardiovascular mortality and 0.64 (95% CI, 0.50-0.83) and 0.67 (95% CI, 0.53-0.85) for all-cause mortality, compared with those in the lowest quartile. A one-standard-deviation increase in hemoglobin and serum iron levels corresponded to a 19% and 24% reduction in cardiovascular mortality risk and a 19% reduction in all-cause mortality risk for both factors. Restricted cubic spline analysis revealed L-shaped and U-shaped associations between hemoglobin and serum iron levels and cardiovascular and all-cause mortality, respectively.

Conclusions: Hemoglobin and serum iron levels were significantly associated with lower risks of cardiovascular and all-cause mortality in patients with CAD. Further research is needed to evaluate the effects of iron supplementation in these patients.

Keywords: coronary artery disease; hemoglobin; iron; mortality; prospective cohort study.

Figure 1

Restricted cubic splines in Cox models of hemoglobin levels with cardiovascular (A) and all-cause (B) mortality risk. Adjustments were made for age; sex; alcohol drinking status; smoking status; body mass index; systolic blood pressure; diastolic blood pressure; fasting plasma glucose; non-high-density lipoprotein cholesterol; triglycerides; duration of coronary artery disease; estimated glomerular filtration rate; type of coronary artery disease (acute and chronic); C-reactive protein; the use of anti-diabetic, anti-platelet, cholesterol-lowering, and anti-hypertensive drugs; and serum iron levels. The middle solid line represents the hazard ratio, while the upper and lower dashed lines indicate the 95% confidence interval.

Figure 2

Restricted cubic splines in Cox models of serum iron levels with cardiovascular (A) and all-cause (B) mortality risk. Adjustments were made for age; sex; alcohol drinking status; smoking status; body mass index; systolic blood pressure; diastolic blood pressure; fasting plasma glucose; non-high-density lipoprotein cholesterol; triglycerides; duration of coronary artery disease; estimated glomerular filtration rate; type of coronary artery disease (acute and chronic); C-reactive protein; the use of anti-diabetic, anti-platelet, cholesterol-lowering, and anti-hypertensive drugs; and hemoglobin levels. The middle solid line represents the hazard ratio, while the upper and lower dashed lines indicate the 95% confidence interval.