Risk Factors of COPD

The most important risk factor for the development of COPD is cigarette smoking, which is associated with 85–90% of all cases. Smokers exhibit a substantially greater rate of annual decline in forced expiratory volume in 1 sec (FEV1) than the normal age-related decline of 15–30 mL/yr. Cigar and pipe smokers are also at increased risk of developing COPD, albeit less than cigarette smokers. However, only a minority (~15%) of smokers develop clinically significant COPD, suggesting that genetic predisposition and other environmental factors may be required for the development of lung injury.
Less than 1% of COPD cases are linked to alpha1-antitrypsin deficiency, a known genetic factor associated with premature development of emphysema that is greatly accelerated by smoking. Alpha1-antitrypsin inhibits neutrophil-derived elastase, an enzyme responsible for the destruction of lung parenchyma in emphysema. Patients with alpha1-antitrypsin deficiency carry a genetic polymorphism leading to decreased alpha1-antitrypsin serum levels, which in homozygous individuals may be <10% of normal. Alpha1-antitrypsin deficiency should be considered in a patient with emphysema who has (a) a minimal smoking history, (b) early onset COPD (<45 yrs), (c) a family history of lung disease, or (d) a predominance of lower lobe emphysema on chest x-ray or CT scan.
Other risk factors for COPD include occupational exposures to dusts and chemicals; pollution (indoor and outdoor), especially the combustion products of biomass fuels; severe respiratory infections in childhood; and poor socioeconomic status (which predisposes the patient to the preceding factors).