Chronic cough may point to more severe asthma phenotype
medwireNews: Among patients with asthma, those with chronic cough have worse respiratory symptoms and lung function, and higher levels of some inflammatory markers, than those without, study findings indicate.
The investigation included 855 patients with asthma from the Copenhagen General Population Study, of whom 8.2% had chronic cough, defined as a cough lasting for more than 8 weeks.
Morten Dahl (Zealand University Hospital, Køge, Denmark) and co-researchers demonstrated that the 70 patients with chronic cough were significantly more likely to report wheezing than the 785 without, at rates of 70% and 54%, respectively.
Moreover, asthma patients with versus without chronic cough had higher rates of other respiratory symptoms, including dyspnoea (74 vs 49%), night-time dyspnoea (27 vs 11%), sputum production (59 vs 14%) and chest pain/tightness (14 vs 4%), report the researchers in The Journal of Allergy and Clinical Immunology: In Practice.
Indeed, “90% of asthmatic individuals with concomitant chronic cough reported accompanying respiratory symptoms, which thereby precludes cough-variant asthma and instead suggests uncontrolled asthma”, the team points out.
Lung function, measured by forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC), was also significantly worse among asthma patients with chronic cough than those without (FEV1= 86 vs 89% predicted; FVC=92 vs 94% predicted).
Additionally, individuals with chronic cough were significantly more likely to have had at least six episodes of acute bronchitis and/or pneumonia in the previous 10 years than those without, at rates of 21% and 10%, respectively, as well as a significantly higher probability of having at least three visits to a primary care provider in the previous year, with corresponding rates of 60% and 45%.
In their analysis of inflammatory markers, the investigators found that asthma patients with chronic cough had significantly higher levels of blood neutrophils and leukocytes, as well as plasma fibrinogen, than those without, but levels of blood eosinophils and plasma high-sensitivity C-reactive protein and immunoglobulin-E antibodies were comparable among the two groups.
Combined, these findings “indicate that chronic cough in individuals with asthma is associated with a more severe disease phenotype”, write Dahl and colleagues.
They note that their study had a number of limitations, including self-reported asthma diagnosis and lack of information on the type and dosage of inhaled medication used.
“[F]uture studies of dosage and type of treatment used for individuals with asthma with concomitant chronic cough therefore seem warranted”, the team concludes.
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