Objective: This study aimed to identify those comorbidities with greatest impact on patient-reported health status in patients with chronic obstructive pulmonary disease (COPD) and to develop a comorbidity index that reflects their combined impact.
Study design and setting: We included 408 Swiss and Dutch primary care patients with COPD from the International Collaborative Effort on Chronic Obstructive Lung Disease: Exacerbation Risk Index Cohorts (ICE COLD ERIC) in this cross-sectional analysis. Primary outcome was the Feeling Thermometer, a patient-reported health status instrument. We assessed the impact of comorbidities at five cohort assessment times using multiple linear regression adjusted for FEV1, retaining comorbidities with associations P ≤ 0.1. We developed an index that reflects strength of association of comorbidities with health status.
Results: Depression (prevalence: 13.0%; regression coefficient: -9.00; 95% CI: -13.52, -4.48), anxiety (prevalence: 11.8%; regression coefficient: -5.53; 95% CI -10.25, -0.81), peripheral artery disease (prevalence: 6.4%; regression coefficient: -5.02; 95% CI-10.64, 0.60), cerebrovascular disease (prevalence: 8.8%; regression coefficient: -4.57; 95% CI -9.43, 0.29), and symptomatic heart disease (prevalence: 20.3%; regression coefficient: -3.81; 95% CI -7.23, -0.39) were most strongly associated with the Feeling Thermometer. These five comorbidities, weighted, compose the COMorbidities in Chronic Obstructive Lung Disease (COMCOLD) index.
Conclusion: The COMCOLD index reflects the combined impact of five important comorbidities from patients' perspective and complements existing comorbidity indices that predict death. It may help clinicians focus on comorbidities affecting patients' health status the most.
Trial registration: ClinicalTrials.gov NCT00706602.
Keywords: Chronic obstructive; Comorbidity; Comorbidity index; Health status; Health-related quality of life; Patient-reported outcome; Pulmonary disease.
Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.