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Does Dysanapsis Increase Risk of COPD?

August 21, 2020
Medically reviewed by Susan Kerrigan, MD and Marianne Madsen
Additions/comments by Pulmonologist Kelly Fan, MD

Scientists have known for years that almost a third of COPD cases are diagnosed in those who have never touched a cigarette. Now there may be an explanation for this phenomenon — another lung condition, called dysanapsis, may play a factor.


What is dysanapsis?


Dysanapsis is a condition that causes one’s airways to be proportionally smaller than their lungs. It is often diagnosed in childhood and usually results in reduced lung capacity and breathing issues. Recently, studies have linked dysanapsis to a higher incidence of COPD, or chronic obstructive pulmonary disease — a disease which also causes progressively worsening breathing issues and is mostly diagnosed in lifelong smokers. This new research shows that patients with dysanapsis are more likely to develop COPD regardless of their smoking status.

Kelly Fan, MD

Obesity is a risk factor for dysanapsis which predisposes to the obstructive physiology seen in asthma and COPD.

The study


Published in June 2020 in the Journal of the American Medical Association (JAMA), the study, which was partly funded by the National Heart, Lung, and Blood Institute (NHLBI), assessed the correlation between dysanapsis and COPD using data from three different studies on lung health: The Multi-Ethnic Study of Atherosclerosis (MESA), the Canadian Cohort of Obstructive Lung Disease (CanCOLD), and the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS). Lung CT scans from over 6,500 older adults were taken from each of these studies.


The study’s team of researchers found that out of the more than 6,500 participants, those with undersized airways and relatively larger lungs (some degree of dysanapsis) had the weakest lung function and the highest risk of COPD. They were also eight times more likely to develop the disease compared to participants without dysanapsis.


“These results show that small airways relative to lung size are a very strong risk factor for COPD,” said Benjamin Smith, MD, pulmonary physician at Columbia University and lead author of the study. “This helps us to understand why 30% of COPD can occur in people who never smoked.”


Smith also noted that the study’s results may bring an answer to another scientific mystery: the fact that many lifelong, heavy smokers do not develop COPD at all. It’s possible that people with larger airways relative to the size of their lungs may have increased protection against some of the harmful effects of tobacco. Since they have a greater lung capacity, they may never encounter COPD, which largely affects one’s breathing.


To sum up


Researchers examined lung data from three different major studies that included more than 6,500 older participants. They found that those who had some degree of dysanapsis (small airways relative to lung size) had an overall weaker lung function and an eight-fold increased risk of developing COPD compared to participants without any lung issues. This association led the researchers to understand why one-third of COPD cases occur in non-smokers.

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