Epidemiology

COPD (chronic obstructive pulmonary disease), a commonly fatal respiratory tract disease, affects half a billion people worldwide. COPD is characterised by a chronic inflammatory reaction to irritants, most commonly cigarette smoke. The loss of the alveolar wall, pulmonary hypertension, and fibrosis of the respiratory epithelium occur as COPD progresses from early beginnings to severe disease. COPD is caused by the interaction of a variety of different risk factors, which can operate alone or in a synergistic manner. The most serious of these is cigarette smoking, which is the leading cause of chronic bronchitis and emphysema. COPD can also be caused by air pollution and certain occupational exposures. The frequency of chronic bronchitis has been linked to poor socioeconomic position in numerous epidemiological studies. Furthermore, endogenous risk factors such as gender, genetic traits, the existence of respiratory problems in childhood, and family history must be considered in the aetiology of COPD. Epidemiologic research has been critical in characterising the disease at a population level, identifying plausible causes, and measuring its impact on individuals and society as a whole to date.