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dc.contributor.authorAhern, Thomas P.en_US
dc.contributor.authorBosco, Jaclyn L. F.en_US
dc.contributor.authorSilliman, Rebecca A.en_US
dc.contributor.authorYood, Marianne Ulcickasen_US
dc.contributor.authorField, Terry S.en_US
dc.contributor.authorWei, Feifeien_US
dc.contributor.authorLash, Timothy L.en_US
dc.date.accessioned2011-12-29T21:02:25Z
dc.date.available2011-12-29T21:02:25Z
dc.date.issued2009-8-9
dc.identifier.citationAhern, 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)
dc.identifier.issn1179-1349
dc.identifier.urihttp://hdl.handle.net/2144/2533
dc.description.abstractBACKGROUND: 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.sponsorshipNational 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.isoenen_US
dc.publisherDove Medical Pressen_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.subjectEpidemiologyen_US
dc.subjectBreast neoplasmsen_US
dc.subjectComorbidityen_US
dc.subjectConfounding factors (epidemiology)en_US
dc.subjectBias (epidemiology)en_US
dc.subjectStatistical modelsen_US
dc.titlePotential Misinterpretations Caused by Collapsing Upper Categories of Comorbidity Indices: An Illustration from a Cohort of Older Breast Cancer Survivorsen_US
dc.typearticleen_US
dc.identifier.pubmedid20865090
dc.identifier.pmcid2943165


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