Greater focus on identifying possible genotype-environmental interactions is needed to help our understanding of how and why chronic obstructive pulmonary disease (COPD) develops, according to a recent review. New ways of determining genotype-environmental interactions in association studies, linkage studies, and family based association analysis should be applied in COPD research, the authors say.

The obvious environmental candidate is cigarette smoke. Other candidates might include respiratory infections, air pollution, and occupational exposure to agents harmful to the lungs.

Cigarette smoke certainly affects COPD in severe α₁ antitrypsin (AAT) deficiency, which is often accompanied by early onset COPD. Smokers with the PI Z AAT deficiency phenotype have more severe COPD which develops earlier than their non-smoker counterparts. A significant genotype-environmental interaction occurs between PI type and pack years of smoking for a study population of index and non-index cases. Exposure to mineral dust in PI Z results in high levels of COPD independently of smoking history.

Smoking and genetic factors may interact in primary relatives of probands with COPD, who historically have higher rates of airflow obstruction and develop early, severe COPD independently of severe AAT deficiency. Primary relatives who are current or ever smokers have significantly lower airflow compared with non-smoker controls whereas primary relatives who have never smoked have similar airflow.

The search for candidate genes—for a whole array of proteases, detoxifying enzymes, antioxidants, and inflammatory mediators—has proved inconclusive or contradictory. It is time to focus on gene-environmental interactions in COPD.

▴Thorax 2002;57:736–741.