Age-Dependent Risk of Long-Term All-Cause Mortality in Patients Post-Myocardial Infarction and Acute Kidney Injury

Objectives: We aimed to investigate the association between acute kidney injury (AKI) and the risk for long-term (up to 10 years) all-cause mortality among elderly compared with younger patients following an acute myocardial infarction (AMI). Methods: This study was a retrospective analysis of the Soroka Acute Myocardial Infarction registry and covered the years 2002 to 2017. It included patients diagnosed with an AMI who had a baseline estimated glomerular filtration rate (eGFR) greater than 60 mL/min/1.73 m² and serum creatinine measurements available during hospitalization. The patients were stratified by age: elderly (aged 65 years or older at admission) and younger. In each stratum, two groups were defined based on the presence of an AKI. The survival approach (Kaplan–Meier survival curves, log-rank test and Cox regressions) was utilized to estimate and compare the probability of long-term (up to 10 years) all-cause mortality in each group. Results: Among the 10,511 eligible patients, which consisted of 6132 younger patients (58.3%) and 4379 elderly (41.7%), an AKI occurred in 15.2% of cases, where the elderly patients experienced a higher incidence than the younger patients (20.9% vs. 11.2%, p < 0.001). The presence of an AKI significantly increased the risk of death in both age groups, with the association being stronger among the younger patients (AdjHR = 1.634, 95% CI: 1.363–1.959, p < 0.001) than among the elderly (AdjHR = 1.278, 95% CI: 1.154–1.415, p < 0.001, p-for-interaction = 0.020). Conclusions: An AKI following an AMI was associated with a high risk for long-term all-cause mortality in both age groups, with a stronger association among younger patients.