Characterisation of the overlap COPD-asthma phenotype. Focus on physical activity and health status.

Background: Patients with COPD may share some clinical characteristics with asthma sufferers. This phenotypic overlap between COPD and asthma is not yet well characterised.

Method: We have analysed data from the EPI-SCAN study, an epidemiological, population-based study in Spain that included 3885 (40 to 80-year-old) subjects in order to investigate the clinical and systemic inflammatory characteristics of COPD patients previously diagnosed with asthma. Generic and COPD-specific quality of life, as well as physical activity, were also assessed through standardised and validated questionnaires.

Results: A total of 385 (10.1%) subjects were diagnosed with COPD, 67 (17.4%) being classified with the COPD-asthma overlap phenotype. Such patients were more likely to have dyspnea and wheezing (p<0.001 in both comparisons) and more frequent exacerbations (p<0.001). No differences in systemic inflammatory markers were observed except for lower NOx concentrations in overlap patients (p=0.013). This overlap phenotype significantly worsened specific quality of life (11.1 units on the St. George's Respiratory Questionnaire (SGRQ), 95%CI: 4.88-17.36) and reduced physical activity (3.49 units on the London Chest Activities of Daily Living (LCADL) scale, 95%CI: 1.06-5.94).

Conclusions: In this population-based study, 17.4% of the individuals identified with COPD had an overlap COPD-asthma phenotype. This patient subgroup had more dyspnea, wheezing, exacerbations, worse respiratory-specific quality of life, and reduced levels of physical activity. Specific interventions may be required to adequately care for this subgroup of patients.