Discriminative Ability of the Charlson Comorbidity Index for Long-Term Mortality in a General Population: Nationwide, Population-Based Study of 10 Million Adults in Sweden.

Background: The Charlson Comorbidity Index (CCI) is widely used to control confounding factors in epidemiological studies. There is a need to characterize the performance of CCI in a contemporary general population. This study assessed the discriminative ability of CCI for long-term mortality in relation to age, sex, data source, length of look-back period, and calendar time. Methods: Open cohort study of all adults residing in Sweden for at least one year between 2003 and 2022. Multiple versions of the CCI were calculated based on 1-10 years of lookback in the Swedish National Patient Register. Discrimination was determined using the concordance index (C-index). Kaplan-Meier curves were used to describe 10-year survival. Results: About 10395689 unique individuals had a median follow-up for mortality of 10 years. The C-index of CCI increased with the length of the look-back period, from 0.694 (95% confidence interval [CI], 0.694-0.694) at 1 year, to 0.784 (95% CI, 0.783-0.784) at 5 years, and to 0.808 (95% CI, 0.807-0.808) at 10 years. Discrimination was highest in subjects aged 60 years, for whom the discrimination of CCI Conclusion: The CCI discriminated risk of death best using a look-back period of at least 5 years and performed better in women than in men in most age groups. Our findings offer insights into both the practical utility of the CCI and the interpretation of studies in which it has been applied.