Nearly Half of China’s Population Suffers from Small Airway Dysfunction


New research from China shows that small airway dysfunction is highly prevalent in the adult population, with cigarette smoking, air pollution exposure, and increase in BMI as major risk factors. These findings were published in a study in the journal The Lancet.

The measurement of small airway function and an early catch of small airway dysfunction can be used for identifying people at a high risk of developing lung disease or for the early diagnosis of several lung diseases.

The study funded by Ministry of Science and Technology of China, National Natural Science Foundation of China and the National Health Commission of China, found out that small airway dysfunction is highly prevalent in the general population. The dysfunction of the airways has several risk factors as well, including cigarette smoking, PM2.5 exposure and increase of BMI by 5 kg/m2.

Source: Respiratory Research

This is especially significant as most of the people who might have this condition may be at increased risk of developing severe or critical COVID-19 as well. The findings suggest that there is an urgent need to develop and implement effective primary and secondary prevention strategies to reduce the burden of this condition in the general population.

Looking through the scientific literature it becomes apparent that not a lot is known about small airway dysfunction in people. To bridge this gap, scientists from china took data from the nationally representative China Pulmonary Health study which invited 57,779 adults to participate using a multistage stratified sampling method from ten provinces.

Among these people nearly 50,479 patients had valid lung function testing results. These people were included in the analysis. The small airway dysfunction was defined on basis of three indicators of lung function being less than 65% of predicted: maximal mid-expiratory flow, forced expiratory flow (FEF) 50%, and FEF 75%. All of these help scientists gauge air capacity of humans.

People who were then diagnosed with the small airway dysfunction were also divided into two categories called pre-small airway dysfunction and post-small airway dysfunction.

The analysis of the data showed that the small airway dysfunction was at 43·5% in the general population. Pre-small airway dysfunction was 25·5% and post-small airway dysfunction was 11·3%.

According to the scientists, in 2015, 426 million adults had small airway dysfunction, 253 million had pre-small airway dysfunction, and 111 million had post-small airway dysfunction in China.

Source: The Lancet

People were more likely to suffer from small airway dysfunction based on their age, gender, urbanization density, education level, cigarette smoking, passive smoking, biomass use, exposure to high particulate matter with a diameter less than 2·5 μm (PM2·5) concentrations, history of chronic cough during childhood, history of childhood pneumonia or bronchitis, parental history of respiratory diseases, and increase of body-mass index (BMI) by 5 kg/m2.

The odds ratios for small airway dysfunction and pre-small airway dysfunction were similar, whereas larger effect sizes were generally seen for post-small airway dysfunction than for either small airway dysfunction or pre-small airway dysfunction.

For post-small airway dysfunction, cigarette smoking, exposure to PM2.5, and increase of BMI by 5 kg/m2 were significantly associated with increased risk, among preventable risk factors. There was also a strong association between cigarette smoking and post-small airway dysfunction among men, but not among women.

All of this led the scientists to suggest that there should be more widespread monitoring and diagnosis of the small airway dysfunction so that in the future serious lung diseases like COPD, asthma, bronchitis, among others can be avoided.

Source: European Respiratory Journal

Small airway dysfunction occurs when the luminal airway diameter becomes less than 2 mm. This increases degree of breathlessness often with age and severity of the issue and is a risk factor for many serious conditions, especially COPD.

Patients with chronic obstructive pulmonary disease (COPD) experience trouble breathing with age due to small airway dysfunction characterized by thickening of the airway wall with epithelial changes, obstruction of airway lumen by mucous and inflammatory exudates, infiltration of the airway wall by inflammatory cells, and increased airway smooth muscle and increased peribronchiolar fibrosis.

Source: Boehringer Ingelheim

People may also suffer from small airway dysfunction due to genetic or developmental issues. In other studies, it has been seen that people who have small airways relative to the size of their lungs may have a lower breathing capacity, which can lead to an increased risk for COPD even if a person does not smoke.

COPD is a disease that makes it harder for people to breathe. It often results in people who have a history of smoking. But one third of the cases are observed in people who do not smoke. This has led the scientists to study the disease and conclude that the main actor behind the disease might be the dysfunction of the small airways of lungs than any other factor.

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