Etiology

Tobacco use (90% of cases)

• Smoking is the major risk factor for COPD, but those who have quit ≥ 10 years ago are not at increased risk.

• Passive smoking

Exposure to air pollution or fine dusts

• Nonorganic dust: such as industrial bronchitis in coal miners

• Organic dust: ↑ incidence of COPD in areas where biomass fuel (e.g., wood, animal dung) is regularly burned indoors

Lung growth and development abnormalities [9]

• Recurrent pulmonary infections and tuberculosis

• Premature birth [10]

α1-Antitrypsin deficiency

Airway hyperresponsiveness

Antibody deficiency syndrome (e.g., IgA deficiency)

Primary ciliary dyskinesia (e.g., Kartagener syndrome)