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Contributed by Dr Patricia Macedo, clinical research fellow, and Dr Omar S Usmani, clinical senior lecturer and honorary consultant physician in respiratory medicine at the National Heart and Lung Institute, Imperial College London & Royal Brompton Hospital NHS Foundation Trust.
Section 1: Epidemiology and aetiology
COPD is a chronic inflammatory condition of the airways and lung parenchyma, characterised by persistent airflow obstruction that is usually irreversible and progressive.1
In contrast, asthma is characterised by variable airflow obstruction that is usually reversible and rarely progressive in severity.
COPD consists of a variable mixture of pathological lung lesions: emphysema with destruction of the alveolar walls and development of airspaces; airways inflammation; mucous gland hyperplasia in larger airways; and fibrosis mainly in smaller airways.
COPD is also associated with extra-pulmonary systemic effects, which may contribute to the severity of disease in individual patients.2
The global economic and social burden of COPD is enormous. By 2020, COPD is expected to increase from the sixth to the third most common cause of death worldwide and become the third most common cause of morbidity.
It has been estimated approximately 2 per cent of the UK population has COPD, but this figure represents the 'tip of the iceberg' as many patients remain undiagnosed.3,4
The single most important risk factor for the development of COPD is cigarette smoking, which causes 80-90 per cent of all cases.
Noxious particles and gases in cigarette smoke cause an irritant immunological and inflammatory response in the airways and lung parenchyma. However, there is large individual susceptibility to the effects of cigarette smoking, as demonstrated by the many smokers ((approx)75 per cent) who never develop significant airflow obstruction and COPD.
Other risk factors include environmental air pollution, occupational exposures (coal and gold mining, cement and cotton industries, cadmium workers), genetics (e.g. alpha-1 antitrypsin deficiency), childhood respiratory illness (predisposes to chronic adult disease), recurrent bronchopulmonary infections, low socioeconomic status, poor diet and chronic asthma.
The burning of indoor biomass cooking …