Inflammatory indices significantly improve one-year mortality prediction in STEMI patients: a large-scale multi-center study

Background Inflammation is crucial to the pathogenesis, progression, and prognosis of ST-segment elevation myocardial infarction (STEMI). Routine complete blood count-derived inflammatory indices—neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), and monocyte-to-lymphocyte ratio (MLR)—are proposed as prognostic markers, but their relative value and incremental contribution beyond conventional risk factors in STEMI patients remain unclear. Purpose To evaluate the association of these inflammatory indices with one-year all-cause mortality in STEMI patients and quantify their incremental prognostic value over a baseline clinical model. Methods This retrospective cohort study enrolled 44,802 consecutive STEMI patients with complete one-year follow-up for all-cause death. NLR, PLR, SII, and MLR were calculated from admission complete blood count results. Cox proportional hazards regression models were constructed to assess the independent association of inflammatory indices with mortality: Model 0 (clinical variables only: age, sex, hypertension, diabetes, prior myocardial infarction [MI]); Model 1 (Model 0 + NLR); Model 2 (Model 0 + NLR + PLR + SII + MLR). Discriminative performance was evaluated using Harrell’s C-index (with standard error [SE]) and receiver operating characteristic (ROC) curves (area under the curve [AUC]) for individual inflammatory indices. All statistical analyses were performed with R software; p <0.05 was considered statistically significant. Results A total of 7,103 deaths occurred, with a one-year mortality rate of 15.85%. All inflammatory indices were independently associated with one-year mortality (all p <0.003). The AUC values of individual indices were modest: NLR and MLR 0.593, PLR 0.587, SII 0.573 (all poor-to-moderate range: 0.50–0.70) (Figure 1). In multivariable Cox analysis, NLR (HR 1.016, 95%CI 1.014–1.019, p <0.001) and MLR (HR 1.192, 95%CI 1.160–1.224, p <0.001) were the strongest predictors. The C-index was 0.663 (SE 0.0031) for Model 0, 0.682 (SE 0.0032, Δ+0.019) for Model 1, and 0.688 (SE 0.0032, Δ+0.025) for Model 2 (Figure 2). Conclusions Inflammatory indices from routine blood tests, especially NLR and MLR, independently predict one-year all-cause mortality in STEMI patients and provide significant incremental prognostic value over conventional risk factors (Δ C-index +0.025). Adding NLR alone improves risk stratification (Δ C-index +0.019). These simple, low-cost markers facilitate early risk stratification and personalized management.Figure 1Figure 2