In a new study, researchers found that people with small airways relative to the size of their lungs may have a lower breathing capacity and, consequently, an increased risk for COPD, even if they don’t smoke or have any other risk factors.
The research was conducted by the National Heart, Lung, and Blood Institute (NHLBI).
Chronic obstructive pulmonary disease (COPD), the fourth leading cause of death in the United States, causes airflow blockage and breathing-related problems that can severely limit a person’s day-to-day activities.
It is a debilitating lung condition and often develops as a result of smoking.
Smoking, asthma, or air pollution account for many COPD cases, but up to 30% of cases occur in people who never smoked, and only a minority of heavy smokers develop the disease, suggesting that there are other risk factors at play.
Previous research offered a clue about a possible cause, finding that about half of older adults with COPD appeared to have low lung function early in life.
Now researchers may finally have an answer—and it may be linked to how lungs develop in certain people.
The team did a careful analysis of lung images of more than 6,500 older adults with COPD and found that an abnormal lung development may account for a large proportion of COPD risk among older adults.
The team says when people breathe, they move air through their airways, beginning with the windpipe or trachea, which branches out to smaller airways called bronchi and bronchioles.
As people grow, their airways are thought to develop in proportion to their lungs, but in some people, the airways grow smaller or larger than expected—a condition called dysanapsis— for reasons that are not clear.
This study showed that participants with smaller airways relative to lung size were much more likely to develop COPD compared with those with the larger airways relative to lung size.
The association remained after considering standard COPD risk factors, including smoking, pollutants, and asthma.
The researchers then found never smokers with COPD had much smaller airways relative to lung size, whereas the heavy smokers who did not have COPD had larger than normal airways.
These results show that small airways relative to lung size are a very strong risk factor for COPD.
This helps scientists to understand why 30% of COPD can occur in people who never smoked.
With normal aging, lung function declines, so people who already have low lung function to begin with may develop COPD later in life, even if they don’t smoke.
The lead author of the study is James Kiley, Ph.D., director of NHLBI’s Division of Lung Diseases.
The study is published in JAMA.
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