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Insurance-related differences in Chronic Conditions Data Warehouse comorbidities of Medicare beneficiaries
Justin M Schaffer1, John J Squiers, Austin Kluis
1Baylor Scott & White, The Heart Hospital-Plano, 4708 Alliance Blvd, Plano, TX 75093.
Insights
Medicare Advantage beneficiaries undergoing CABG have fewer documented comorbidities, leading to biased survival estimates when this difference isn't accounted for in analyses.
Area of Science:
- Health Services Research
- Biostatistics
- Cardiovascular Surgery
Background:
- Medicare beneficiaries enrolled in Medicare Advantage (MA) plans have different patterns of documented comorbidities compared to those in traditional Medicare (TM).
- The Chronic Conditions Data Warehouse (CCW) is a key data source for Medicare outcomes research, but its documentation of comorbidities may vary by insurance type.
Purpose of the Study:
- To assess the prevalence of comorbidities documented in the CCW among Medicare beneficiaries undergoing coronary artery bypass grafting (CABG).
- To demonstrate how disparities in comorbidity documentation between MA and TM plans can introduce information bias into outcomes research.
Main Methods:
- Retrospective cohort study of 1,158,701 Medicare beneficiaries who underwent CABG between 2008 and 2019.
- Compared CCW-reported comorbidity prevalence between MA and TM enrollees.
- Used overlap propensity score weighting for risk adjustment, with and without CCW comorbidity data, to compare median survival.
Main Results:
- The proportion of CABG recipients in MA plans increased from 17.5% to 38.3% between 2008 and 2019.
- MA enrollees had significantly fewer CCW-documented comorbidities than TM enrollees (standardized mean difference of 0.431).
- Risk adjustment including CCW comorbidities led to substantially lower estimated median survival for MA enrollees (9.52 years) compared to TM enrollees (10.91 years), unlike analyses without comorbidity data.
Conclusions:
- Significant differences exist in CCW-documented comorbidity prevalence between MA and TM beneficiaries undergoing CABG.
- Failure to account for these insurance-related documentation differences can cause substantial bias in risk-adjusted analyses.
- Medicare outcomes research using CCW data must address these disparities to avoid biased treatment effect estimates and inform accurate clinical or policy decisions.
Objectives:
To demonstrate the prevalence of comorbidities documented by Chronic Conditions Data Warehouse (CCW) data for Medicare beneficiaries and to illustrate how failing to account for differences in reported comorbidities can result in information bias.
Study Design:
Retrospective cohort study of Medicare beneficiaries who underwent coronary artery bypass grafting (CABG) between 2008 and 2019.
Methods:
A total of 1,158,701 Medicare beneficiaries underwent CABG. The prevalence of CCW-reported comorbidities was compared between beneficiaries enrolled in Medicare Advantage (MA) or traditional Medicare (TM) plans. Median survival differences (with 95% CIs) were compared in unadjusted and risk-adjusted analyses using overlap propensity score weighting, with and without inclusion of CCW-reported comorbidities during risk adjustment.
Results:
The proportion of MA-enrolled CABG recipients increased annually from 17.5% in 2008 to 38.3% in 2019. MA-enrolled beneficiaries had fewer CCW-reported comorbidities than TM-enrolled beneficiaries (average standardized mean difference across 27 CCW comorbidities, 0.431). After risk adjustment for demographics, median survival differed minimally between MA- and TM-enrolled beneficiaries (10.00 vs 10.05 years; difference, -15 [95% CI, -41 to 13] days). However, when CCW-reported comorbidity data were included in risk adjustment, MA-enrolled beneficiaries demonstrated substantially lower median survival (9.52 vs 10.91 years; difference, -507 [95% CI, -538 to -466] days).
Conclusions:
The prevalence of CCW-reported comorbidities differs significantly between TM-enrolled and MA-enrolled beneficiaries who underwent CABG. These differences can introduce substantial bias in risk-adjusted analyses that erroneously assume equivalent CCW-reported comorbidity documentation across insurance types. Medicare outcomes research that relies on CCW-reported comorbidity data without accounting for insurance-related differences may produce biased treatment-effect estimates, potentially misinforming clinical or policy decisions.
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