Certain changes in a gene called ADAM33 can determine whether a smoker is likely to develop chronic obstructive pulmonary disease (COPD) or not, new research indicates.

COPD, a progressive disease that makes it hard to breathe, can cause coughing that produces large amounts of mucus, wheezing, shortness of breath, chest tightness, and other symptoms.

Cigarette smoking is the leading cause of COPD - most people who have COPD smoke or used to smoke, but it is also associated with long-term exposure to other lung irritants, such as air pollution and chemical fumes.

The two main components are emphysema and chronic obstructive bronchitis, which both damage the walls of the lung, making breathing difficult.

In the journal Respiratory Research, Dr. Alireza Sadeghnejad, from Wake Forest School of Medicine, Winston-Salem, North Carolina, and colleagues report that certain changes in ADAM33 increase the risk of COPD in smokers.

Only about a quarter of long-term smokers develop COPD, the authors note. ADAM33 has been shown in previous studies to be associated with asthma and overreactive airways. This relationship, however, has not been studied in tobacco smokers who are susceptible to COPD.

In the new study, the research team looked for small genetic changes or “polymorphisms” in ADAM33 in 880 long-term heavy smokers.

Two hundred eighty-seven of the study subjects had COPD and 311 did not. All of them were older than age 50 years and all had been smoking at least a pack of cigarettes each day for 20 years. Ninety-seven percent of the subjects were male.

Sadeghnejad and colleagues identified five genetic changes in ADAM33 that occurred more frequently in the COPD group than in the group of smokers without COPD.

The investigators say that further studies are needed to determine how these changes impact the symptoms and course of COPD.

SOURCE: Respiratory Research, March 12th online, 2009.