Abstract
Background: Many statistical analyses, clinical trials and cost-utility analyses designed to measure the impact of a particular disease on utility scores often overlook the important influence of co-morbidity burden.
Objectives: This study aims to examine the impact of co-morbidity burden on EQ-5D index scores in a nationally representative sample of the US.
Methods: The pooled 2001 and 2003 Medical Expenditure Panel Survey was used. The total number of chronic conditions for each individual was calculated based on Clinical Classification Categories codes. Spline regression was used to identify nonlinear age effects: individuals were separated into four quartiles based on age. Censored least absolute deviation was used to regress EQ-5D index scores on age and chronic co-morbidity, controlling for income, gender, race, ethnicity, education, physical activity and smoking status. Interactions between age and chronic conditions were also explored.
Results: The coefficients for chronic co-morbidities were highly statistically significant with large magnitudes for those with two or more chronic conditions (coefficient two chronic conditions=-0.16; coefficient nine chronic conditions=-0.28). After controlling for chronic co-morbidities and other confounders, age was not statistically significant except for those aged >58 years and the magnitude of this coefficient was very small (coefficient aged >58 years=-0.0006). The interactions between age and chronic comorbidity were significant, but the deleterious impact of their interaction was largely dominated by the existence and number of chronic conditions.
Conclusions: Chronic conditions have a significant deleterious impact on EQ-5D index scores that is much more pronounced than age and other sociodemographic and behavioural characteristics. Future analyses and costutility models should incorporate the impact of multiple morbidity.
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Acknowledgments
Funding was provided by the National Institute on Aging (grant no. 1R03AG027348-01). The authors had complete authority over design and conduct of the study; management, analysis and interpretation of the data; and preparation, review and approval of the manuscript.
All authors meet the following criteria: (i) conceived and planned the work that led to the manuscript or played an important role in the acquisition, analysis and interpretation of the data or both; (ii) wrote the paper and/or made substantive suggestions for revision; and (iii) approved the final submitted version. The corresponding author (P.W. Sullivan) takes responsibility for the work as a whole.
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Sullivan, P.W., Ghushchyan, V.H. & Bayliss, E.A. The Impact of Co-Morbidity Burden on Preference-Based Health-Related Quality of Life in the United States. PharmacoEconomics 30, 431–442 (2012). https://doi.org/10.2165/11586840-000000000-00000
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DOI: https://doi.org/10.2165/11586840-000000000-00000