Abstract
Background: In COPD research little consideration is currently given to the impact of co-existing comorbidities, which is partly due to the absence of an index that would quantify their impact. We developed a COPD comorbidity index that quantifies the impact on health-related quality of life (HRQL).
Methods: Using data from 411 Swiss and Dutch COPD patients with GOLD stages ≥2 we used the non-COPD specific Feeling Thermometer (FT, scores 0-100) as a valid and reliable instrument to measure HRQL. We ascertained the presence of comorbidities that may impact on HRQL through self-report and chart review. In the analysis, we used specific comorbidities if their prevalence was ≥5% and summarized rarer comorbidities by disease groups (e.g. psychiatric disease). We included theses diseases in multivariate linear regression models if their association with the FT was ≥3 points (=0.5 minimal important difference) in univariate analysis adjusted for FEV1.
Results: Coronary heart disease (p=0.018), diabetes (p=0.009), psychiatric disease (p=0.017) and urogenital disease (p=0.018) were most strongly associated with HRQL in the final multivariate model, which was then transformed into an index ranging from 0-4 where each disease counted equally. An increase of one disease count was associated with a decrease in HRQL of -4.54 on the FT (95% CI -6.34 to -2.74, p<0.001).
Conclusion: A simple index that counts the presence of four comorbidities can be used to quantify the impact of comorbidities in COPD patients in research and practice.
- © 2011 ERS