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Subfreezing air as cough trigger may signal asthma in chronic cough

People whose cough triggers include subfreezing air, along with other factors, may point to the presence of asthma in those with chronic cough, according to a Finnish study published in Respiratory Medicine.

“The typical manifestations of the cough hypersensitivity syndrome are the increased cough sensitivity to known tussigens, like exhaust fumes (hypertussia), and cough that is triggered in response to a nontussive stimulus, like exercise (allotussia). These triggers of cough are generally considered nonspecific and are not utilized in current cough guidelines to identify cough background disorders. However, there are some reports suggesting that certain cough triggers may be specifically associated with certain cough background disorders. The present study was conducted to investigate this possibility in a large community-based sample of well-characterized subjects with chronic cough,” the researchers wrote.

For the study, the researchers emailed public service employees in two towns in Finland and invited them to participate in an electronic questionnaire about 12 cough triggers. Of the 3,697 respondents (mean age, 47.8 years; 82.6% women), 421 had chronic cough, defined as current cough lasting longer than 8 weeks.

Among those with chronic cough, the prevalence of cough triggers was highest among people with asthma, followed by those with chronic rhinitis, gastroesophageal reflux and idiopathic cough.

Subfreezing air as a cough trigger was linked to an increased likelihood of having current asthma (adjusted OR = 7.27; 95% CI, 4.09-12.9). Additionally, for separating people with current asthma from others with chronic cough, the presence of subfreezing air as a cough trigger had a sensitivity of 82%, a specificity of 62%, a positive predictive value of 42% and a negative predictive value of 92%.

“This association can be best explained by the special hypersensitivity of the asthmatic airways to the sudden rise in airway lining fluid osmolarity,” the researchers wrote.

The number of cough triggers was also greatest in people with asthma (mean, 7.05), followed by people with chronic rhinitis (mean, 4.94), gastroesophageal reflux (mean, 4.6) and idiopathic cough (mean, 3.44; P < .001 for all).

Having at least five triggers was associated with increased likelihood for current asthma (aOR = 7.49; 95% CI, 3.96-14.2), whereas the absence of any cough trigger was tied to increased odds for idiopathic cough (aOR = 2.71; 95% CI, 1.54-4.77).

Further, the presence of at least five cough triggers had a sensitivity of 87% and a specificity of 58% to separate people with current asthma from others with chronic cough. The positive predictive value was 40% and the negative predictive value was 93%.

The researchers noted, however, that the list of triggers included in the study may not be comprehensive and, because the study was conducted in Finland, the results may not be applicable to those living in warmer climates.

“These findings may help in the clinical management of chronic cough, which relies on the identification of the most probable cough background disorder. Prospective studies are now needed to test the validity of these conclusions,” they wrote. – by Melissa Foster

Disclosures: This work was supported by the foundations Kuopion Seudun Hengityssäätiö and Hengityssairauksien Tutkimussäätiö. The authors report no relevant financial disclosures.