Nordic Multimorbidity Index, Charlson, Elixhauser and count-based comorbidity indices for mortality risk: a...

The aim of the present study was to compare Area Under the Receiver Operating Characteristic curves (AUROCs) of age-and-sex alone, and in addition respectively, the Nordic Multimorbidity Index (NMI), Charlson Comorbidity Index (CCI) and Elixhauser Comorbidity Index (ECI), and explore simple count-based measures on in-patient care and filled drug prescriptions, with the outcome mortality using Swedish health registries.

Study population: All persons born in 1975 or earlier who were continuously resident in Sweden between 1 January 2010 and 31 December 2014 (n=5 010 261) with a follow-up for all-cause mortality from 1 January 2015 to 31 December 2019.

AUROCs were calculated with 1- to 5-year-look-back for age-and-sex, each index and explored measures for 1- to 5-year mortality.

AUROC was for age-and-sex alone for 5-year mortality 0.8731. Age-and-sex alone outperformed, respectively: NMI, difference in AUROC, 0.0695 (95% CI 0.0687 to 0.0704); CCI, 0.1509 (95% CI 0.1500 to 0.1518) and ECI 0.1631 (95% CI 0.1622 to 0.1640). AUROC for NMI when added to age-and-sex, 0.9072 was marginally higher than age-and-sex alone. AUROC for explored measures as numbers of hospitalisations, days hospitalised, or numbers of filled drug prescriptions were around 0.75-0.80 and when added to age-and-sex around 0.90.

Age-and-sex alone showed higher AUROC than any other measure alone and NMI provides modest additional discrimination, with CCI and ECI both less helpful, that is, informative. Explored measures; days hospitalised or numbers of filled prescriptions rendered AUROC of somewhat lower magnitude when added to age-and-sex. Thus, the latter could be considered for use in addition to age-and-sex when full background data are lacking.