Prognostic Impact of Laboratory Frailty Index in Elderly Patients with Acute Myocardial Infarction: A Retrospective Cohort Study

Abstract Background: Acute myocardial infarction (AMI) is a leading cause of death in the elderly. Frailty syndrome is associated with adverse outcomes. The Laboratory Frailty Index (FI-LAB) provides an objective assessment of frailty, but its prognostic value in older AMI patients remains inadequately investigated. Methods: This retrospective cohort study utilized the MIMIC-IV database and enrolled 3,257 AMI patients aged ≥65 years. The FI-LAB was calculated from 27 laboratory parameters within 24 hours of admission, and patients were stratified into quartiles (Q1-Q4). The primary outcome was in-hospital mortality. Secondary outcomes included 30-day, 90-day, and 360-day all-cause mortality. Multivariable Cox regression, Kaplan-Meier analysis, and ROC curves were used to evaluate the predictive performance of FI-LAB. Results: The median patient age ranged from 76.14 to 77.54 years, with the proportion of females decreasing from 47.66% in Q1 to 64.18% in Q4. In-hospital mortality increased significantly across FI-LAB quartiles (Q1: 8.09% vs. Q4: 28.06%, p