Researchers have discovered that genetic variations in the anatomy of the lungs could serve as indicators to help identify people who have low, but stable, lung function early in life, and those who are particularly at risk for chronic obstructive pulmonary disease (COPD) because of a smoke-induced decline in lung function. The results of the study, which was funded by the National Heart, Lung and Blood Institute (NHLBI), part of the National Institutes of Health, appear this week in the journal Proceedings of the National Academy of Sciences.
Cigarette smoking has long been the most common cause of COPD, but not all smokers develop the condition, and many non-smokers do. Why that is so has never been fully understood, but a team of researchers now have a clue after discovering that genetically programmed airway tree variation is linked to a higher prevalence of COPD among older adults.
“This novel study suggests that a CT scan, which is widely available, can be used to measure airway structure and predict who is at higher risk for smoke-induced lung injury,” said James Kiley, MD, director of the NHLBI Division of Lung Diseases.
“In the current study, we found that central airway branches of the lungs, which are believed to form early in life, do not follow the textbook pattern in one quarter of the adult population and these nontextbook variations in airway branches are associated with higher COPD prevalence among older adults,” said the study’s first author Benjamin Smith, MD, MS, assistant professor at Columbia University Medical Center. “Interestingly, one of the airway branch variants was associated with COPD among smokers and nonsmokers. The other was associated with COPD, but only among smokers.”
These airway tree variations are identifiable on low-dose screening lung CT scans, which are currently indicated clinically for lung cancer screening in older patients with a history of heavy smoking in the prior 15 years. Before CT scans are used outside of this group for the identification of airway variants in clinical practice, the study authors say more research will be needed to confirm that preventive or therapeutic interventions based on the presence of airway tree variations can improve patients’ outcomes.
In the meantime, the researchers say they will be investigating another important finding: family history. Their study identified a common airway branch variation that occurs within families and is associated with COPD among nonsmokers. Smith said while other developmental events that occur within families may be involved, his research team is looking into whether there is a genetic basis for this variant.
The researcher emphasized that for all the new findings, quitting smoking remains the best antidote to COPD, and smokers trying to quit should seek professional help, if necessary, to succeed.