Abstract
Frailty indices derived from electronic health records offer an efficient approach to identify vulnerable individuals in the general population. We aimed to validate the electronic-regional healthcare database frailty index (e-RHD-FI) in the general adult population, describe its distribution by sex and age, evaluate its predictive validity for mortality, hospitalization and fragility fractures, and assess the performance of frailty cut-off points. We conducted a population-based study of 8,404,004 adult beneficiaries of the Lombardy Regional Health System. The e-RHD-FI was calculated from 40 health deficits using electronic health records from 2008 to 2018. We assessed its distribution, predictive validity for 1-year mortality, hospitalizations and fragility fractures through multi-state analysis and multivariable models evaluating performance across subgroups. The e-RHD-FI distribution was highly asymmetrical (median 0.0125, first-third quartiles 0-0.0375), with 45.8% of adults having no deficits. The index was higher in older adults. Each 0.1-point increment in e-RHD-FI was associated with doubled 1-year mortality risk (HR 2.12, 99% CI 2.11-2.14), 2.5-fold increased hospitalization rate (IRR 2.51, 99% CI 2.49-2.53), and a 55% higher risk of fragility fracture (HR 1.55, 99% CI 1.53-1.57). The AUC for 1-year mortality was 0.883 (99% CI 0.881-0.884). The e-RHD-FI demonstrates strong predictive validity for adverse outcomes in the general population and can effectively identify at-risk individuals for targeted interventions.