Chronic Obstructive Pulmonary Disorder can affect non-smokers too; smaller airways may be to blame, finds study
A group of scientists concluded that smaller airways relative to lung size is a strong risk factor for COPD as these people would already have low lung function from the beginning.
We all know someone who has never smoked a day in their life but still complains of breathing issues. According to the National Institute of Health of the US, amongst the total reported cases of Chronic Obstructive Pulmonary Disorder (COPD) in the United States, around 30 percent of them are the ones who never smoked.
This fact has often raised the question as to why some non-smokers despite following a healthy lifestyle, suffer from respiratory issues such as asthma and COPD, while some heavy smokers never experience those disease. Now it seems like scientists might have found the reason behind this.
COPD, a deadly lung disease
Chronic Obstructive Pulmonary Disorder, commonly called COPD, is a lung disease which worsens the condition of the lungs progressively, making it difficult for one to breathe. According to the global burden of disease report of 2017, COPD is one of the diseases that account for more that one million deaths worldwide every year. COPD involves two conditions: emphysema and bronchitis.
In emphysema, the walls between the air sacs of the lungs (alveoli) are damaged which makes the air sacs floppy. This also damages the walls of the air sacs resulting in the destruction of the smaller air sacs that are necessary for the exchange of gases. All of this makes it difficult for one to breathe.
In chronic bronchitis, there is constant irritation and inflammation of the lining of the airways. This leads to the formation of thick mucus in the airway, making it difficult to breathe.
Investigations based on COPD
To find out the cause behind the prevalence of COPD in non-smokers, Dr Benjamin Smith, a pulmonary physician at Columbia University Irving Medical Center in New York City, and his team looked up at three studies on COPD including more than 6,500 participants. The three studies were:
1. The Multi-Ethnic Study of Atherosclerosis (MESA) Lung Study included people from six cities who were age 69 on average.
2. The Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS) included people from 12 US medical centres who were age 63 on average.
3. The Canadian Cohort of Obstructive Lung Disease (CanCOLD) study included people from nine Canadian cities who were age 67 on average.
During the study, the researchers took CT scans of the lungs of these patients.
The reason for COPD in non-smokers
The results of these studies showed signs of dysanapsis in people. When we breathe in, the air travels from the nose or mouth to the windpipe and then goes to the lungs while travelling through the smaller branched structures called bronchi and bronchioles. As the lungs grow with age, the airway develops accordingly. However, in some cases, the airway grows smaller or larger than expected, which is medically called dysanapsis.
The MESA Lung and CanCOLD studies concluded that some of the people showed dysanapsis with smaller airways, thus they were more likely to develop COPD compared with those with the larger airways relative to lung size.
The researchers then compared the participants from the CanCOLD study, who never smoked, and the participants from the SPIROMICS study, who were heavy smokers. The comparison showed that people who never smoked but had COPD had smaller airways relative to lung size, whereas the heavy smokers who did not have COPD had larger than normal airways.
The scientists thus concluded that smaller airways relative to lung size is a strong risk factor for COPD as these people would already have low lung function from the beginning.
For more information, read our article on COPD (Chronic Obstructive Pulmonary Disease).
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