Tobacco smoking

Tobacco smoking causes 80% to 90% of COPD cases. Smokers are more than ten times as likely to die from COPD than non-smokers (US DHHS, 2004). Chemicals found in tobacco smoke stimulate inflammation in the lungs, leading to destruction of the alveoli and narrowing of the airways. While smoking is related to most COPD cases, only 15% to 20% of smokers develop the disease.

Environmental factors

Exposure to outdoor and indoor air pollutants increases the prevalence of COPD by an estimated 2% for each 10 g/m3 increase in particulate matter (Künzli, 1997). The use of biomass fuels (e.g. use of wood for cooking and heating) increases the risk of COPD by three to four times, contributing significantly to COPD prevalence, especially in rural regions (Halbert et al., 2003).

Age

COPD is rarely found below the age of 40 (Halbert et al., 2003). Lung function deteriorates with age. Ageing may therefore increase the susceptibility for the development of COPD and its exacerbations. As previously stated, COPD prevalence is higher in elderly people; it is not the physiological decline of the function which predispose to COPD.

Sex

Sex does not seem to have a specific meaning in the development of COPD in the general population, except when related to smoking behaviour. Male smoking rates still exceed female, although prevalence rates for European women are increasing while male rates have either reached a plateau or are decreasing. It is likely that the COPD prevalence will follow this pattern.

Recent research indicates that estrogen plays a role in maintaining the lung function in women, putting postmenopausal women at higher risk of developing COPD, having a severe form, and dying from COPD. This may explain the higher prevalence of COPD among older women non-smokers, compared to the male non-smoking population (Massaro & Massaro, 2004).

Genetic factors

A rare inherited condition and the only currently known genetic risk factor for COPD, alpha1-antitrypsin (AAT) deficiency is due to the inability to produce enough of the lung-protective protein AAT in the liver. Severe AAT-deficiency leads to emphysema at an early age.

Socio-economic inequalities

Deprivation, measured by income and education can negatively affect lung function, independently of smoking. Underlying reasons include childhood infections, occupational exposure and poor housing conditions. Impaired lung function can increase the susceptibility to COPD and its exacerbations (Pauwels, 2000).