# Mediating role of systemic inflammation in linking transferrin saturation to all-cause mortality in patients with coronary artery disease: Evidence from a large population-based study

## TL;DR

This study finds that transferrin saturation has a U-shaped link to mortality in heart disease patients, with inflammation playing a key role in the lower range.

## Contribution

The novel finding is that systemic inflammation partially mediates the relationship between low transferrin saturation and mortality in coronary artery disease.

## Key findings

- Transferrin saturation shows a U-shaped relationship with mortality in CAD patients.
- Systemic inflammation markers partially mediate the mortality risk at low transferrin saturation levels.
- Maintaining transferrin saturation between 20-30% may reduce mortality risk in CAD patients.

## Abstract

Transferrin saturation (TS) is associated with mortality across populations, but its nonlinear relationship with all-cause mortality in coronary artery disease (CAD) and the role of systemic inflammation remain unclear. This study explored the association between TS and mortality in CAD patients, focusing on systemic inflammation as a potential mediator.

Data from National Health and Nutrition Examination Survey (NHANES) 1999–2006 included 769 CAD patients (>18 years) with available TS and mortality records. Systemic inflammation markers, such as the systemic immune-inflammation index (SII) and systemic inflammation response index (SIRI), were analyzed. Kaplan–Meier curves, Cox proportional hazards models, and mediation analyses examined the interactions between TS, inflammation, and mortality.

A U-shaped relationship between TS and all-cause mortality was observed, with an inflection point at 30.5%. TS levels ≤30.5% were inversely associated with mortality (HR = 0.98; 95% CI, 0.96–0.99; P < 0.0001), while levels >30.5% increased mortality risk (HR = 1.05; 95% CI, 1.02–1.08; P < 0.001). Systemic inflammation markers (SII/SIRI) were associated with and may partially mediate the relationship between low TS (≤30.5%) and mortality. (mediation proportions: 28.5% and 21.8%, respectively). No mediation effects were found for TS > 30.5%.

TS demonstrates a U-shaped relationship with all-cause mortality in CAD patients. Systemic inflammation is linked to both TS and mortality outcomes, suggesting potential mechanistic interplay. Maintaining TS within 20–30% and addressing inflammation may reduce mortality risk.