Objectives: Several frailty indices have been constructed to identify frail older people at increased risk of mortality and admission. Previously, we have developed a claims-based multimorbidity frailty index (mFI) using Taiwan’s National Health Insurance Research Database (NHIRD). As the ICD-10 coding system was adopted to replace the previous ICD-9-CM system in Taiwan in 2016, it is necessary to renew the mFI using ICD-10 codes and assess the types of deficits and their association with clinical outcomes.

Methods: Subjects aged 65 to 100 years with full National Health Insurance coverage in 2017 were included. We constructed the renewed mFI using ICD-10 codes (mFI-v10) by the cumulative deficit approach and categorized the subjects according to the mFI-v10 quartiles: fit,mild frailty,moderate frailty,and severe frailty. Multivariate Cox proportional hazard models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (95% CIs) of mFI-v10 on outcomes of interest (1-year mortality,unplanned hospitalization,and intensive care unit (ICU) admission),adjusted by sex and age.

Results:The mFI-v10 incorporated 38 deficits with mean mFI-v10 score of 0.051 (standard deviation = 0.048) among 144,567 subjects.Compared with the fit group, those with severe frailty were associated with a 4-fold (adjusted HR 3.86, 95% CI 3.54-4.20) higher risk for death at one year. Subjects with moderate frailty or mild frailty were associated with a 2.4-fold (adjusted HR 2.35, 95% CI 2.18–2.55) or 1.6-fold (adjusted HR 1.57, 95% CI 1.47–1.69) higher risk for death at one year than the fit group.Similar risk trends can also be observed in unplanned hospitalization and ICU (intensive care unit) admission among the study population.

Conclusion:The renewed multimorbidity frailty index constructed from ICD-10 codes is associated with an increased risk of 1-year of all-cause mortality, unplanned hospitalization, and ICU admission. It can provide updated information contributing to risk stratification using frailty index in the ICD-10 era.