Comorbid asthma and associations with patient-related outcomes in COPD

Background: Clinical features of COPD and asthma can be similar and make differential diagnostics difficult. Our aims were to explore prevalence of comorbid asthma in COPD and associations with patient-related outcomes. Methods: Patients with a doctor’s diagnosis of COPD were randomly selected in two cohorts in 2005 (n = 1060) and 2014 (n = 1668), from primary and secondary care in Sweden. Data were collected from medical records and patient questionnaires at baseline and at follow-up of each cohort in 2012 and 2022, respectively. The questionnaires included data on exacerbations, medication and symptoms using the clinical COPD questionnaire (CCQ) and the modified Medical Research Council (mMRC) dyspnoea score. Patients with a recorded doctor’s diagnosis of comorbid asthma were identified in both cohorts. Mortality data for the 2005 cohort were obtained up till July 2021. Logistic regression explored patient-reported outcomes and Cox regression analysed mortality risk, during follow-up. Results: The prevalence of comorbid asthma was 22% in the 2005 cohort and 9% in the 2014 cohort (p<0.001). Comorbid asthma was associated with increased risk of exacerbations in both cohorts, adjusted odds ratio (OR) (95%CI) 1.58 (1.07–2.32), p=0.02 and 2.52 (1.42–4.47), p=0.002. In the 2014 cohort comorbid asthma was associated with more frequent use of short-acting β2-agonists, OR (95%CI) 2.49 (1.27–4.87), p=0.008. COPD with comorbid asthma was not associated with a higher risk of mortality, hazard ratio (95%CI) 0.93 (0.76-1.15). Discussion: The prevalence of comorbid asthma in COPD has decreased. We speculate this is potentially due to more careful diagnostic procedures. Comorbid asthma is still an important factor to consider, as it could be associated with a higher risk of exacerbations.