Association between the aggregate index of systemic inflammation and 28- or 365-day mortality in acute myocardial infarction patients: insights from the MIMIC-IV database

Systemic inflammation plays a key role in acute myocardial infarction (AMI). The Aggregate Index of Systemic Inflammation (AISI), a composite measure of neutrophils, monocytes, platelets, and lymphocytes, may offer a more comprehensive assessment of inflammation than single biomarkers. However, its association with short- and long-term mortality in AMI patients remains underexplored. This retrospective study analyzed data from 969 AMI patients in the Medical Information Mart for Intensive Care(MIMIC) -IV database, stratified by AISI levels into tertiles. Cox regression and Kaplan-Meier survival analyses assessed the relationship between AISI and mortality. Subgroup analyses examined age, gender, and comorbidity effects, and the predictive value of AISI was evaluated using Receiver Operating Characteristic(ROC) curves. This study enrolled 969 patients with AMI, stratified into group1(low), group2(medium), and group3(high) tertiles. The group3 exhibited significantly higher 28-day mortality (18.6% vs. 5.6% in low/medium groups) and 365-day mortality (27.2% vs. 13.3% in the low group) (both P < 0.001). Survival analysis demonstrated an inverse correlation between AISI levels and survival probability (P < 0.001). Restricted cubic spline(RCS) models revealed a nonlinear association between AISI and mortality (28-day: likelihood ratio test P = 0.001; 365-day: P = 0.002). Multivariable Cox regression confirmed a dose-response relationship between AISI tertiles and mortality risk (trend P < 0.001 for both endpoints). Subgroup analyses highlighted greater sensitivity to AISI in female patients (28-day: interaction P = 0.041; 365-day: P = 0.011), with ROC curve analysis showing enhanced predictive performance in females (28-day AUC: 0.759 vs. 0.669, P = 0.019; 365-day AUC: 0.760 vs. 0.730, P = 0.038). In this study, AISI exhibited a nonlinear association with 28-day and 365-day mortality in AMI patients. Higher AISI levels were significantly linked to increased mortality risk. Notably, female patients showed greater sensitivity to elevated AISI, suggesting its potential value in risk stratification and clinical management.