Heterogeneity of perception of symptoms in patients with asthma

Cough-dominant or cough-variant asthma is common in Japan. However, it is unclear whether cough and dyspnea, the cardinal symptoms of bronchial asthma, are similarly perceived, and whether these symptoms are linked to pulmonary function tests.

The subjects were 548 physician-diagnosed naive patients with asthma. Visual analogue scale (VAS) scores were determined and spirometry was performed before and after 1-month inhaled corticosteroid/long-acting beta2 agonist therapy.

The patients were divided into those with a significant bronchodilating response and an increase in FEV₁ (>12% and >200 mL) after treatment (n=146); and nonresponders without this response (n=402). Cough was more dominant than dyspnea in both groups at the initial evaluation. Both symptoms were diminished after treatment, but scores for cough remained significantly higher than those for dyspnea in nonresponders. VAS scores for dyspnea at both time points differed in responders and nonresponders, and changes of cough and dyspnea scores were larger in responders. In responders, peak expiratory flow (PEF) (absolute, %predicted) for cough and FEV₁ (%predicted), VC (%predicted) and PEF (absolute) for dyspnea were correlated at both time points, but in nonresponders, neither cough nor dyspnea was related to a common spirometric parameter at both time points. Changes in cough and dyspnea scores were correlated with changes of FEV₁ (absolute, %predicted) and FEF_25-75 (absolute) for responders, while only PEF (%predicted) was correlated with these changes in nonresponders. Calculated slopes (ΔVAS score/ΔFEV₁) suggested that responders were more sensitive to dyspnea than nonresponders.

Perception of cough and dyspnea were similar, but not identical, for bronchodilating responders and nonresponders among patients with bronchial asthma. Linkage of pulmonary function parameters with perceptions of cough and dyspnea also differed between the responders and nonresponders.