Frailty as a Key Determinant of In-Hospital Mortality in 58,040 Patients with Community-Acquired Pneumonia: Evidence from a Chilean Cohort

<b>Background:</b> Pneumonia is a leading cause of hospitalization and death among older adults, reflecting both patient vulnerability and the quality of acute care. However, evidence from Latin America remains limited. <b>Objective:</b> to examine the association between frailty level assessed using the HFRS and in-hospital mortality among older adults hospitalized with community-acquired pneumonia (CAP). <b>Methods:</b> We conducted a retrospective cohort study using the Chilean National Health Fund (Fondo Nacional de Salud, FONASA) database, including patients aged ≥ 60 years hospitalized with CAP (ICD-10 codes J12-J18) between 2019 and 2024. Variables analyzed included age, sex, frailty level assessed by the Hospital Frailty Risk Score (HFRS), comorbidity burden (Charlson Comorbidity Index), Diagnosis-Related Group (DRG) severity level, and relative weight. Survival was analyzed using Kaplan-Meier curves and log-rank tests. Multivariable Cox proportional hazards models estimated adjusted hazard ratios (HR) with 95% confidence intervals (CI). <b>Results:</b> The cohort comprised 58,040 patients (51.2% women). Overall, in-hospital mortality was 19.3%. Independent predictors of mortality included advanced age (≥90 years: HR = 2.41; 95% CI: 2.27-2.56), male sex (HR = 1.10; 95% CI: 1.06-1.14), high frailty risk (HR = 1.57; 95% CI: 1.47-1.68), and greater DRG severity (per level: HR = 1.66; 95% CI: 1.58-1.73). The Charlson Comorbidity Index lost significance after adjustment. <b>Conclusions:</b> Frailty emerged as a strong and independent determinant of in-hospital mortality in older adults with CAP. Systematic frailty assessment combined with comorbidity indices could improve risk stratification and guide more personalized, evidence-based clinical management in acute care settings.