Abstract
BACKGROUND: Pneumonia remains a major cause of hospitalization and death among older adults worldwide. Simple bedside biomarkers that capture the host response to infection may help support early risk stratification in routine care. The fibrinogen-to-albumin ratio (FAR) integrates information on inflammation, coagulation, and nutritional status. We explored whether the admission FAR is associated with 30- and 365-day all-cause mortality in older adults hospitalized with pneumonia. METHODS: We conducted a single-center retrospective cohort study of patients aged ≥ 65 years who presented to a fever clinic with acute fever and were subsequently admitted to general medical wards with radiologically confirmed pneumonia in 2021. FAR was calculated from fibrinogen and albumin measured within 24 h of admission. Associations between FAR and 30- and 365-day all-cause mortality were analyzed using multivariable Cox regression and restricted cubic splines. RESULTS: Of the 339 included older adults with pneumonia, 47 (13.9%) died within 30 days and 78 (23.0%) died within 365 days after admission. In fully adjusted Cox models, a higher admission FAR was associated with increased mortality, with a hazard ratio (HR) per 0.10-unit increase of 1.62 (95% CI, 1.07–2.46) for 30-day all-cause mortality and 1.39 (95% CI, 1.00–1.94) for 365-day all-cause mortality. Restricted cubic spline analyses supported a generally increasing risk of death with a higher FAR at both time points, without strong evidence of marked nonlinearity. CONCLUSIONS: Among older adults hospitalized with pneumonia, a higher FAR at admission was associated with increased 30-day and 365-day all-cause mortality, with a stronger association for short-term mortality. FAR may represent a simple, routinely available biomarker of adverse prognosis in this population, but prospective studies are needed to confirm its clinical utility. TRIAL REGISTRATION: Not applicable. This retrospective study was not prospectively registered. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12879-026-12520-6.