Association between the age-to-serum albumin ratio and all-cause mortality in patients with acute myocardial infarction: a retrospective cohort study

Background Acute myocardial infarction (AMI) remains a predominant cause of cardiovascular death, necessitating accurate risk stratification. Existing risk scores like the ACEF (Age, Creatinine, Ejection Fraction) score and GRACE (Global Registry of Acute Coronary Events) score have limitations in complexity and subjectivity. This study aimed to investigate the novel age-to-serum albumin ratio (A2A Index) as a simple, objective predictive marker for all-cause mortality in AMI patients. Methods The A2A Index was retrospectively calculated by dividing age by serum albumin in 1,007 consecutively enrolled AMI patients with 4-year median follow-up. The association between the A2A Index and all-cause mortality was assessed using Kaplan–Meier survival analysis, Cox regression analysis, and restricted cubic spline. The predictive performance of the A2A Index was compared with the ACEF and GRACE scores. Results The A2A Index was capable of independently predicting all-cause mortality after multivariable adjustment hazard ratio (HR) 4.98 per one-unit increase in A2A Index; 95% CI: 3.34–7.43; P 0.001. Restricted cubic splines illustrated a significant J-shaped dose-response relationship between the A2A Index and all-cause mortality risk ( P -nonlinearity 0.001). The A2A Index showed comparable discrimination to ACEF score area under the curve (AUC): 0.83 vs. 0.83; P = 0.656 and superior to GRACE score (AUC: 0.83 vs. 0.80; P = 0.041), with a good calibration ( χ 2 = 9.08; P = 0.336). The optimal cutoff value for the A2A Index was 1.86, with a sensitivity of 79% and a specificity of 70%. Conclusion The A2A Index is a simple and independent predictor of all-cause mortality in AMI patients, superior to GRACE score and comparable to ACEF score, with 1.86 indicating high mortality risk.