The Charlson Comorbidity Index: problems with use in epidemiological research

  • Allison Drosdowsky
    Corresponding author. Peter MacCallum Cancer Centre, Department of Health Services Research, Locked Bag 1, A'Beckett St, Melbourne, Victoria, Australia. Tel.: +61-3-8559-7842; fax: +61-3-8559-5909.
    Department of Health Services Research, Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
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  • Karla Gough
    Department of Health Services Research, Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia

    Department of Nursing, Faculty of Medicine, Dentistry, and Health Sciences, The University of Melbourne, Parkville, Victoria 3010, Australia
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      The Charlson Comorbidity Index (CCI) is a highly cited and well established tool for measuring comorbidity in clinical research, but there are problems with its use in practice. Like most comorbidity summary measures, the CCI was developed to adjust for prognostic comorbidities in statistical models, particularly those exploring associations between a risk of death or survival time and other patient-related and disease-related factors. Despite this, the CCI is often used in cancer research to measure all comorbidity, or as a multimorbidity measure, and CCI scores are often used to assess the prognostic importance of multiple health conditions. In the latter case, it is not at all surprising that researchers report a significant association between CCI scores and a risk of death or survival times because CCI scores provide a summary of the presence or absence of a set of prognostic comorbidities. Advances in multimorbidity research require specific attention to the methods used to develop relevant indices. Published literature on the association between the comorbidity and risk of death or survival time should be interpreted with caution, especially if the CCI was used to provide a measure of comorbidities.


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