Comorbid asthma – occurrence and associations with patient-related outcomes in COPD: a cohort study

Purpose: Clinical features of COPD and asthma overlap, complicating differential diagnosis. This study investigated the prevalence of comorbid asthma in COPD patients and its association with patient-related outcomes.Materials and methods: Patients with a doctor’s diagnosis of COPD were randomly selected in two cohorts 2005 (n = 1060) and 2014 (n = 1671), from primary and secondary care in Sweden. Data were collected from medical records and patient questionnaires at baseline and at follow-up (2012 and 2022, respectively). Questionnaires included data on exacerbations. Symptoms were assessed using the clinical COPD questionnaire (CCQ). Comorbid asthma was identified through medical records. Ten-year mortality data were obtained from national registers. Logistic and linear regression assessed associations with patient-reported outcomes; Cox regression was applied for mortality analyses.Results: Comorbid asthma was found in 22% of the 2005 cohort and 9% of the 2014 cohort (p < .001). In both cohorts, it was associated with an increased risk of exacerbations: OR (95% CI) 1.58 (1.07–2.32), p = .02, and 2.20 (1.38–3.52), p < .001, respectively. No associations were found between comorbid asthma and worsening of health status (CCQ). Mortality risk did not differ in the 2005 cohort, HR (95% CI) 0.92 (0.71–1.18), but was lower in the 2014 cohort, HR (95% CI) 0.67 (0.49–0.93), p = .02.Conclusion: Comorbid asthma in COPD has changed from 22 to 9%, potentially due to improved diagnostics. Comorbid asthma remains clinically relevant due to its association with an increased exacerbation risk.