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Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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The most important cause of COPD is smoking.

  • around half of all cigarette smokers will have some airflow obstruction present while 10 -20% will develop clinically significant COPD.
  • pipe and cigar smoking is also associated with a significant increase in morbidity and mortality (but the risk is less than for cigarette smokers)
  • an increased risk of COPD in passive smokers or environmental tobacco smoke (ETS) has also been observed in several case-controlled studies (1)

Other causes include:

  • indoor air pollution
    • caused by burning of wood, animal dung, crop residues, coal burnt in open fires or in poorly functioning stoves
    • from biomass cooking and heating in poorly vented dwelling
  • occupational exposure to toxins, e.g. coal dust and cadmium
    • is an under-appreciated risk factor of COPD
    • the risk was estimated to be 20% in diagnosed COPD cases but in lifelong non-smokers this number is increased to 30% (2)
    • the risk of developing COPD is significantly increased in cigarette smokers who are exposed to occupational toxins (3)
  • outdoor air pollution, e.g. exhaust fumes,
    • its role in COPD is unclear, appears to have a relatively small effect in causing COPD
  • genetic factors
    • mutations in the SERPINA1 gene that leads to hereditary deficiency of alpha-1-antitrypsin (AATD) (2)
    • is the best-documented genetic risk factor and is seen in only 1-2% of patients with COPD
    • premature and accelerated development of COPD in both smokers and non-smokers is linked with severe deficiency of α1- antitrypsin.
    • patients who are less than 40 years with severe COPD should be investigated for alpha-1-antitrypsin status since in more than half of patients there is a deficiency (2)
  • infections
    • childhood infections, e.g. measles or whooping cough, are associated with reduced lung function and increased respiratory symptoms in adulthood
    • acute infections cause exacerbation of COPD
  • lung growth and development
    • factors which occur during gestation, birth, and exposures during childhood and adolescence increase the risk of developing COPD
  • socioeconomic status
    • risk of developing COPD is seen in people with lower socioeconomic status
  • asthma and airway hyper-reactivity
    • increased risk of developing chronic airflow limitations and COPD is seen in asthma patients
  • chronic bronchitis
    • various studies have reported an association between mucous hypersecretion and increased FEV1 decline
    • an increased risk of developing COPD is observed in younger adults with chronic bronchitis who smoke (1,2)


  1. Currie, G.P. (Ed.) (2011) ABC of COPD. Oxford: Blackwell Publishing
  2. Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2024. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease

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