A new discovery could someday help identify smokers at risk for chronic obstructive pulmonary disease (COPD), the fourth leading cause of death in the United States.
More than 12 million people in the U.S. have been diagnosed with COPD, and another 12 million may have the condition and not know it. These people have difficulty breathing due to excessive inflammation in their lungs that has narrowed their airways.
The cause of the inflammation is usually prolonged exposure to an inhaled irritant, most often cigarette smoke. Nine out of ten COPD deaths can be attributed to smoking.
Links with COPD, Smoking and Lung Cancer
But even though most people with COPD are current or former smokers, not every smoker gets COPD. Only about 20% will develop the disease, suggesting that there might be genetic factors that make some smokers more susceptible than others.
New research, published yesterday in the journal PLoS Genetics, suggests that variation in a genetic region on chromosome 15 previously linked to nicotine addiction, lung cancer, and peripheral artery disease might also increase the risk for COPD. In light of the mounting evidence for the importance of this stretch of DNA, the authors of the new report suggest that genetic screening of smokers in order to find those at the highest risk may be an attractive interventional strategy.
Sreekumar Pillai, a scientist at GlaxoSmithKline, and colleagues from several research institutions studied a total of more than 5,000 people with European ancestry and found that a SNP on chromosome 15 increased odds of COPD by about 1.3 times. They also found another SNP increased the odds of COPD by about 1.4 times. The two SNPs are very close to each other and probably both mark the same variation affecting COPD risk, although the authors did not test this.
Research has shown that in smokers, each one of the variants is also associated with smoking one more cigarette per day. Whether is linked to lung cancer and peripheral artery disease because of or in addition to its effects on smoking has been controversial.
The authors of the current study say that while their data does not allow them to solve this dilemma with regard to the effects of the chromosome 15 SNPs on COPD, several aspects of their study indicate that the genetic variation has a direct effect on the disease, independent of smoking behavior.
The authors do note, however, that in some subsets of their study population the effect of the riskier versions of the genetic variations was greater in current smokers compared to former smokers. This could mean that people who have a harder time quitting are more likely to develop COPD. Alternatively, it could be the case that some people are at higher risk for COPD if they continue to smoke.
The researchers also found evidence for variations contributing to COPD on chromosome 4, although the results were not statistically significant. However, this same region of DNA was correlated with lung function in a different report in same issue of PLoS Genetics. Both research groups pointed out that the nearest gene to the chromosome 4 variations they identified is involved in lung development, suggesting that future research targeting these variations might reveal more insight into COPD and other lung diseases.