The identification of DNA-sequence variations in a new study of chronic obstructive pulmonary disease (COPD) has researchers theorizing that genetic influences may explain why one-quarter of smokers develop the disease while the rest aren't afflicted, HealthDay News reported March 11.

Researchers from the Wake Forest University School of Medicine and Saint Louis University examined a gene called ADAM33 in 880 long-term, heavy smokers with and without COPD. Variation in ADAM33 had been shown to be important in the development of asthma and altered lung function.

The researchers discovered five single nucleotide polymorphisms -- or DNA sequence variations -- that were more common among the smokers with COPD and could be related to the development of the disease.

"Functional studies will be needed to evaluate the biologic significance of these polymorphisms in the pathogenesis of COPD," the authors wrote.

The study appeared in the March 2009 issue of the journal Respiratory Research.