Chronic bronchitis linked to poor asthma outcomes

Researchers have found that chronic bronchitis is associated with worse clinical outcomes in asthma, particularly among smokers.

In the study, published in Respiratory Medicine, 20% of 59 never smokers with asthma reported chronic bronchitis, or chronic mucus hypersecretion, as did 56% of 61 smokers with asthma.

And these patients differed from those without bronchitis, with poorer asthma control observed among smokers with chronic bronchitis (mean Asthma Control Questionnaire [ACQ] score 2.29 vs 1.57), while never smokers with chronic bronchitis were more likely to have required emergency oral corticosteroids in the previous year (58.3% vs 19.1%). Asthma control was particularly poor among smokers with severe asthma and chronic bronchitis, who had a mean ACQ score of 2.9 versus 1.9 in never smokers with severe asthma and chronic bronchitis.

“Smokers with asthma are known to have worse ACQ scores than never smokers with asthma and possibly a history of chronic mucus hypersecretion adversely effects the perception of symptoms in this sub-group of patients, particularly in those with severe disease,” suggest authors Neil Thomson (University of Glasgow, UK) and colleagues.

They also found that smokers with severe asthma and chronic bronchitis had reduced airway lumen area on computed tomography compared with never smokers with severe asthma and similar symptoms (mean 11.4 vs 18.4 mm²), which the team says may be related to mucus accumulation and bronchodilator use.

However, there was no difference in induced sputum neutrophil and eosinophil counts between patients with and without chronic bronchitis, despite previous studies showing that smokers with asthma have elevated goblet cell levels and more mucus-positive epithelium than ex- and never-smokers.

Thomson and colleagues say that their findings are in line with those showing chronic bronchitis is associated with worse clinical outcomes and increased mortality in patients with chronic obstructive pulmonary disease. Additionally, forced expiratory volume in 1 second has previously been shown to decline more rapidly in smokers with asthma and chronic bronchitis.

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