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Potential Misinterpretations Caused by Collapsing Upper Categories of Comorbidity Indices: An Illustration from a Cohort of Older Breast Cancer Survivors

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dc.contributor.author Ahern, Thomas P en_US
dc.contributor.author Bosco, Jaclyn LF en_US
dc.contributor.author Silliman, Rebecca A en_US
dc.contributor.author Yood, Marianne Ulcickas en_US
dc.contributor.author Field, Terry S en_US
dc.contributor.author Wei, Feifei en_US
dc.contributor.author Lash, Timothy L en_US
dc.date.accessioned 2011-12-29T21:02:25Z
dc.date.available 2011-12-29T21:02:25Z
dc.date.issued 2009-8-9 en_US
dc.identifier.citation Ahern, Thomas P, Jaclyn LF Bosco, Rebecca A Silliman, Marianne Ulcickas Yood, Terry S Field, Feifei Wei, Timothy L Lash. "Potential misinterpretations caused by collapsing upper categories of comorbidity indices: An illustration from a cohort of older breast cancer survivors" Clinical Epidemiology 1:93-100. (2009) en_US
dc.identifier.issn 1179-1349 en_US
dc.identifier.uri http://hdl.handle.net/2144/2533
dc.description.abstract BACKGROUND: Comorbidity indices summarize complex medical histories into concise ordinal scales, facilitating stratification and regression in epidemiologic analyses. Low subject prevalence in the highest strata of a comorbidity index often prompts combination of upper categories into a single stratum ('collapsing'). OBJECTIVE: We use data from a breast cancer cohort to illustrate potential inferential errors resulting from collapsing a comorbidity index. METHODS: Starting from a full index (0, 1, 2, 3, and ≥4 comorbidities), we sequentially collapsed upper categories to yield three collapsed categorizations. The full and collapsed categorizations were applied to analyses of (1) the association between comorbidity and all-cause mortality, wherein comorbidity was the exposure; (2) the association between older age and all-cause mortality, wherein comorbidity was a candidate confounder or effect modifier. RESULTS: Collapsing the index attenuated the association between comorbidity and mortality (risk ratio, full versus dichotomized categorization: 4.6 vs 2.1), reduced the apparent magnitude of confounding by comorbidity of the age/mortality association (relative risk due to confounding, full versus dichotomized categorization: 1.14 vs 1.09), and obscured modification of the association between age and mortality on both the absolute and relative scales. CONCLUSIONS: Collapsing categories of a comorbidity index can alter inferences concerning comorbidity as an exposure, confounder and effect modifier. en_US
dc.description.sponsorship National Cancer Institute (R01 CA 093772, R01 CA 118708, K05 CA 092395); Congressional Directed Medical Research Programs pre-doctoral training award (BC073012) en_US
dc.language.iso en en_US
dc.publisher Dove Medical Press en_US
dc.rights © 2009 Ahern et al, publisher and licensee Dove Medical Press Ltd. This is an Open Access article which permits unrestricted noncommercial use, provided the original work is properly cited. en_US
dc.subject Epidemiology en_US
dc.subject Breast neoplasms en_US
dc.subject Comorbidity en_US
dc.subject Confounding factors (epidemiologic) en_US
dc.subject Bias (epidemiologic) en_US
dc.subject Statistical models en_US
dc.title Potential Misinterpretations Caused by Collapsing Upper Categories of Comorbidity Indices: An Illustration from a Cohort of Older Breast Cancer Survivors en_US
dc.type article en_US
dc.identifier.pubmedid 20865090 en_US
dc.identifier.pmcid 2943165 en_US


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