National Norms for the Elixhauser and Charlson Comorbidity Indexes Among Hospitalized Adults

Background Comorbidity burden is commonly measured among hospitalized adults, yet the U.S. national norms for 2 commonly used comorbidity indexes have not yet been reported. Thus, this study reports U.S. national norms for both Charlson Comorbidity Index (CCI) and the Elixhauser Comorbidity Index (ECI) among hospitalized adults based on age, biological sex, and race. Methods A retrospective observational cohort study using data from the Agency of Healthcare Research and Quality U.S. National Inpatient Sample database for 2017. Patient data were extracted from 7 159 694 inpatient adults, and analyses were focused on individuals older than 45 years, yielding 4 370 225 patients. International Classification of Diseases, 10th Edition, diagnostic codes were used to calculate CCI and ECI scores. These scores were then weighted for the U.S. national population. Results The weighted mean CCI was 1.22 (95% confidence interval [CI]: 1.22, 1.22), and the weighted mean ECI was 2.76 (95% CI: 2.76, 2.76). Both indexes had increasing average scores with increasing age, independent of sex and race (all p values < .001). Conclusion For the first time, U.S. national norms for the CCI and ECI are reported for adult inpatients. The norms can serve as a reference tool for determining if clinical and research populations have greater or lesser comorbidity burden than typical hospitalized adults in the United States for their age, sex, and race.