Influence of comorbid heart disease on dyspnea and health status in patients with COPD - a cohort study

Purpose: The aim of this study was to examine the changing influence over time of comorbid heart disease on symptoms and health status in patients with COPD. Patients and methods: This is a prospective cohort study of 495 COPD patients with a baseline in 2005 and follow-up in 2012. The study population was divided into three groups: patients without heart disease (no-HD), those diagnosed with heart disease during the study period (new-HD) and those with heart disease at baseline (HD). Symptoms were measured using the mMRC. Health status was measured using the Clinical COPD Questionnaire (CCQ) and the COPD Assessment Test (CAT; only available in 2012). Logistic regression with mMRC $2 and linear regression with CCQ and CAT scores in 2012 as dependent variables were performed unadjusted, adjusted for potential confounders, and additionally adjusted for baseline mMRC, respectively, CCQ scores. Results: Mean mMRC worsened from 2005 to 2012 as follows: for the no-HD group from 1.8 (+/- 1.3) to 2.0 (+/- 1.4), (P=0.003), for new-HD from 2.2 (+/- 1.3) to 2.4 (+/- 1.4), (P=0.16), and for HD from 2.2 (+/- 1.3) to 2.5 (+/- 1.4), (P=0.03). In logistic regression adjusted for potential confounding factors, HD (OR 1.71; 95% CI: 1.03-2.86) was associated with mMRC $ 2. Health status worsened from mean CCQ as follows: for no-HD from 1.9 (+/- 1.2) to 2.1 (+/- 1.3) with (P=0.01), for new-HD from 2.3 (+/- 1.5) to 2.6 (+/- 1.6) with (P=0.07), and for HD from 2.4 (+/- 1.1) to 2.5 (+/- 1.2) with (P=0.57). In linear regression adjusted for potential confounders, HD (regression coefficient 0.12; 95% CI: 0.04-5.91) and new-HD (0.15; 0.89-5.92) were associated with higher CAT scores. In CCQ functional state domain, new-HD (0.14; 0.18-1.16) and HD (0.12; 0.04-0.92) were associated with higher scores. After additional correction for baseline mMRC and CCQ, no statistically significant associations were found. Conclusion: Heart disease contributes to lower health status and higher symptom burden in COPD but does not accelerate the worsening over time