• Chronic obstructive pulmonary disease
• COPD epidemiology
• COPD mechanism
• disease classification
• smoking
• spirometry

Chronic obstructive pulmonary disease (COPD) is the diagnostic label given to patients with chronic airflow obstruction that is poorly reversible.1 As such, it is a non-specific disease entity and, like stroke or atrial fibrillation, can be the end result of multiple and often very differing conditions. A diagnosis of COPD based on spirometry alone should therefore trigger further investigation to identify the underlying cause and the application, if possible, of a more appropriate and specific diagnostic label. Hence while sarcoidosis, chronic asthma, organ-specific autoimmune disease, cystic fibrosis and multiple other pathologies can all cause COPD (and in a technical sense allow all such patients to be labelled as having COPD) most would recognise this as diagnostic duplicity.

Recent studies have highlighted the apparently high proportion of patients with COPD who have never smoked. Collectively, these studies suggest that even in developed countries cigarette smoking causes COPD in only 50–70% of patients. Indeed, the Swedish OLIN and US NHANES III studies reported that the population-attributable risk of COPD from smoking in these countries was …