Methods
Subjects
We assessed 520 patients with COPD, which was confirmed with spirometry and 150 controls, either current or ex-smokers free from cardiorespiratory and inflammatory diseases.14 This was a cross-sectional analysis from an ongoing longitudinal study of comorbidities and cardiovascular risk in COPD, Assessment of Risk in Chronic Airways Disease Evaluation (ARCADE, Clinical Trials No NCT 01656421). Patients were recruited when clinically stable and at least 4 weeks from an exacerbation of respiratory symptoms and free from other inflammatory diseases such as rheumatoid arthritis and inflammatory bowel disease. Controls were recruited from previous research databases carried out at the research centre and participant’s relatives. The inclusion and exclusion criteria were previously published in the protocol paper of the ARCADE study.15 All the subjects gave written informed consent, and the study had approval from the South East Wales Research Ethics Committee.