People with asthma who also have bronchiectasis are at greater risk of severe disease and exacerbations, and more likely to be admitted to the hospital, compared with patients without bronchiectasis, a review of published studies found. Such patients also seem to have poorer lung function and more severe airway obstruction.
But more research is needed before definitive conclusions are drawn, the researchers said.
The study, “How does comorbid bronchiectasis affect asthmatic patients? A meta-analysis,” was published in the Journal of Asthma.
Bronchiectasis and asthma are two different diseases that often co-occur in patients. Asthma is a condition in which the airways narrow and swell, making breathing more difficult. An irreversible, progressive disease, bronchiectasis may develop as a consequence of asthma-related inflammation and narrowing of the bronchi in the lungs.
Close to three-quarters of people with asthma also have symptoms of bronchiectasis, previous research has found. But exactly how bronchiectasis impacts the prognosis of asthma patients remains largely unknown.
To find out, researchers at the Shanghai Jiao Tong University Medical School-affiliated Ruijin Hospital, in China, gathered data from several published studies on this topic.
Only six studies met the predefined inclusion criteria for this analysis. Among the total 1,004 patients included in these studies, 385 had both asthma and bronchiectasis, and 619 had asthma but not bronchiectasis. The prevalence of bronchiectasis in this population was 35.2%.
Overall, people with co-occurring bronchiectasis were 3.75 years older and had asthma for almost six more years than those without bronchiectasis. These differences between the groups were statistically significant.
The three studies reporting the severity of asthma showed that people with bronchiectasis were 3.6 times more likely to present with greater asthma severity. These individuals also experienced 0.71 more exacerbations in the previous year than people without bronchiectasis and their risk of hospitalization was about 2.3 times higher.
Those with both conditions also showed poorer lung function and more severe airway obstruction, as assessed by lower scores in the percent predicted forced expiratory volume in one second (FEV1%), forced vital capacity (FVC%), and the ratio of these two measures.
Forced expiratory volume or FEV measures how much air a person can exhale during a forced breath. The amount of air exhaled may be measured during the first (FEV1), second (FEV2), and/or third seconds (FEV3) of the forced breath. Meanwhile, forced vital capacity or FVC is the total amount of air exhaled during the FEV test.
However, a statistical analysis showed that studies looking for lung function had significant publication bias, meaning that studies not finding an association were less likely to be published.
The researchers also noted that people with bronchiectasis had higher levels of immunoglobulin E and tended to have more immune cells called eosinophils, both of which participate in asthma attacks.
Taken together, the present analysis showed that asthmatic patients with comorbid or concurrent bronchiectasis “were older and had a longer disease duration, and showed greater severity,” the researchers wrote, adding that it is possible that inflammation and mucus production caused by severe asthma lead to bronchiectasis.
“However, it is difficult to determine if the severity of asthma in subjects with coexistent bronchiectasis is due to the presence of bronchiectasis, or if the presence of bronchiectasis is a manifestation of the severity of asthma itself,” they wrote.
The team said that the publication bias, as well as the studies’ small number and heterogeneity, were clear limitations to their analysis. Also, parameters that may influence clinical outcomes, such as microbial presence in sputum, treatment, and gas exchange, were not examined.
“Despite the limitations, this meta-analysis emphasizes the effect of bronchiectasis on asthmatic patients in several directions,” the investigators wrote. “Coexistence of bronchiectasis should be considered as a pathological phenotype [disease manifestation] of asthma, which may add to the asthma severity, and increase the risk of exacerbation and hospitalization.”