ALB and myocardial infarction: This study yielded several key findings: (1) the age-to-serum albumin ratio (A2A Index) was first proposed as a strong and independent predictor of all-cause mortality in patients with acute myocardial infarction (AMI); (2) the A2A Index demonstrated a significant non-linear, J-shaped association with mortality risk, with a critical threshold at 1.86, beyond which high risk of mortality in patients with AMI; (3) the A2A Index outperformed the GRACE score and was comparable to the ACEF score, demonstrating excellent discrimination and calibration.