People with obstructive lung diseases, such as asthma and COPD, commonly report respiratory symptoms, including shortness of breath, chronic cough, chronic phlegm, and wheezing. Small airways disease is an important feature of both conditions, where the airways of the lungs that are less than 2mm in diameter become narrowed due to inflammation. Damage to the small airways is thought to precede the development of more severe lung disease. Therefore, the measurement of small airways function has implications for early detection and prevention of disease. Spirometric small airways obstruction (SAO) is a term used to describe obstruction of the small airways detected using a lung function test called spirometry. We conducted a study to investigate whether people with SAO are more likely to report respiratory symptoms, have a history of cardiometabolic disease, and a lower quality of life, even in the absence of established lung disease. We used data from 21,934 participants of the multinational Burden of Obstructive Lung Disease (BOLD) study. All participants performed spirometry before and after inhalation of salbutamol, which is a medication designed to open the airways. Participants completed a questionnaire which enabled us to collect information on their history of shortness of breath, chronic cough, chronic phlegm, and wheezing, as well as cardiovascular disease, hypertension, and diabetes. They also provided us information about their physical and mental quality of life.
We found that approximately 1 in 5 participants had SAO. Participants with SAO were 2-3 times more likely to report shortness of breath, chronic cough, chronic phlegm, and wheezing compared to those without SAO. In addition, we found that participants with SAO were approximately 30% more likely to have a history of cardiovascular disease but not diabetes or hypertension. We also found that physical and mental quality of life were lower in individuals with SAO. These results were also true in people who had never smoked.
We also investigated whether these findings were true among study participants with SAO but with ‘normal’ lung function and, in general, they were. The main difference was that these participants’ quality of life was unaffected
Although the spirometry parameters used to define SAO have long been considered of little use clinically, we have shown that spirometric SAO is not only common in general populations but is associated with outcomes of clinical interest. Further studies are needed to replicate our findings, as well as to investigate whether those with SAO are more likely to develop more serious lung disease in later life.
The manuscript published in Respiratory Research is available here: https://doi.org/10.1186/s12931-023-02450-1