Frailty attenuates the prognostic impact of age in acute myocardial infarction

Background Age is a well-known risk factor for adverse outcomes in acute myocardial infarction (AMI). Frailty, reflecting diminished physiological reserve, may modify the effect of chronological age on prognosis. We aimed to evaluate whether frailty attenuates the association between age and mortality in AMI patients. Methods We conducted a retrospective cohort study of consecutive AMI patients admitted between January 2010 and 2024 across 82 hospitals. Frailty was assessed using the Hospital Frailty Risk Score (HFRS ≥5). Patients were categorized by age (<65, 65–74, ≥75 years) and frailty status. The non-frail group included 53,586, 19,106, and 27,176 patients aged <65, 65–74, and ≥75 years, respectively; the frail group included 17,573, 22,399, and 18,000 patients. Primary outcomes were in-hospital and 1-year all-cause mortality. Multivariable logistic regression and Cox proportional hazards models estimated adjusted odds ratios (aOR) and hazard ratios (aHR) with 95% confidence intervals (CI), stratified by frailty. Results Among non-frail patients, age ≥75 years was associated with higher in-hospital mortality (aOR=2.64, 95% CI: 2.29–3.05, p<0.001) and 1-year mortality (aHR=3.72, 95% CI: 3.42–4.05, p<0.001) compared with age <65 years. In frail patients, the association between age and mortality was substantially attenuated: age ≥75 years had an aOR of 1.81 (95% CI: 1.64–2.00, p<0.001) for in-hospital mortality and an aHR of 2.14 (95% CI: 2.01–2.27, p<0.001) for 1-year mortality. Differences between the 65–74 and <65 years groups were also diminished. Conclusions Frailty attenuates the prognostic impact of age in AMI patients. In frail individuals, chronological age is less predictive of mortality, highlighting the importance of routine frailty assessment to guide risk stratification and individualized management.