The main cause of COPD is smoking. In Canada, smoking causes over 80% of COPD cases. The longer and heavier a person smokes, the higher their risk.

Other causes of COPD include:

  • alpha-1 antitrypsin deficiency (a rare genetic condition)
  • long-term exposure to air pollution, dust, chemicals, and fumes
  • second-hand smoke

COPD takes years to develop, so it is more common in people 55 and over.