Population-Based Validation of a Frailty Index Using Electronic Regional Healthcare Records for Public Health Use

Background 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 and hospitalization, and assess the performance of frailty cut–off points. Methods 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 2008–2018. We assessed its distribution, predictive validity for 1–year mortality and hospitalizations through multi–state analysis and multivariable models evaluating performance across subgroups. Results 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) and 2.5–fold increased hospitalization rate (IRR: 2.51, 99%CI: 2.49–2.53). The AUC for 1–year mortality was 0.883 (99%CI: 0.881–0.884). Conclusions 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.