aetiology
Last edited 04/2018 and last reviewed 02/2021
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 cigarettes smokers)
- an increased risk of COPD in passive smokers or environmental tobacco smoke (ETS) have 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
- such as severe hereditary deficiency of alpha-1-antitrypsin (AATD)
- 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 the 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 α1- antitrypsin status since in more than half of patients there is a deficiency (2)
- infections
- childhood infections, e.g. measles or whooping cough is 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)
Reference:
alpha -1 - antitrypsin deficiency
allergic bronchopulmonary aspergillosis
beta blockers and COPD (chronic obstructive pulmonary disease)