Evaluation of Hospital Readmission and Mortality Risk in Older Frail Patients Using the FIB ‐4 Index: A Cohort Study

Background: Recurrent hospitalizations and mortality are frequent among frail older adults, reflecting reduced physiological reserve and vulnerability to stressors. Identifying inexpensive and readily available biomarkers for risk stratification remains a priority in geriatric medicine. The Fibrosis-4 (FIB-4) index, originally developed to estimate liver fibrosis, has recently emerged as a systemic risk marker beyond hepatic disease. Methods: We conducted a prospective observational study including 248 hospitalized patients aged ≥ 70 years admitted to an internal medicine department. Frailty was assessed using the Frailty Index (FI), which was calculated at hospital admission. The primary composite endpoint was all-cause mortality or unplanned hospital readmission during follow-up (mean 159 ± 128 days). Results: Participants were categorized as low FIB-4 (< 1.3, n = 53) or intermediate–high FIB-4 (≥ 1.3, n = 195). Individuals with FIB-4 ≥ 1.3 showed higher inflammatory burden (increased C-reactive protein), lower nutritional reserve (reduced pre-albumin), higher D-dimer levels, and longer hospital stay. During follow-up, 128 events occurred (39 deaths and 89 readmissions). FIB-4 ≥ 1.3 was associated with increased risk of the composite endpoint (HR 2.268, 95% CI 1.210–4.252, p = 0.011). After adjustment for sex, smoking status, BMI, and frailty index, FIB-4 remained independently associated with adverse outcomes (HR 2.045, 95% CI 1.206–4.199, p = 0.016). Conclusions: FIB-4 appears to reflect reduced biological reserve and systemic vulnerability rather than isolated liver dysfunction. As a cost-free parameter derived from routine blood tests, FIB-4 may represent a practical tool for risk stratification in hospitalized frail older adults.