Longitudinal decline in pulmonary function in atopic cough and cough variant asthma

Objective Cough variant asthma and atopic cough are different clinical manifestations of eosinophilic airway inflammation presenting with isolated chronic non-productive cough. The aim of this study was to examine the longitudinal change in pulmonary function in cough variant asthma and atopic cough. Methods Longitudinal change in FEV1 was prospectively examined in 20 patients with cough variant asthma, 14 patients with atopic cough and 271 asymptomatic healthy subjects. All were lifetime non-smokers. Of the 20 cough variant asthma patients, 13 were taking long-term inhaled corticosteroid therapy (ICS) (beclomethasone dipropionate 615 +/- 58 mug/day) and the other seven were not. Spirometry was taken at first visit, after cough was almost completely relieved on therapy, and at least once every year for 5 or more years afterwards. Results The slope of longitudinal change in FEV1 was not significantly different among cough variant asthma patients (- 0.029 +/- 0.007/year), atopic cough patients (- 0.021 +/- 0.022/year) and asymptomatic subjects (- 0.028 +/- 0.002 L/year). In patients with cough variant asthma, the slope in patients not taking inhaled corticosteroids (ICS) was 0.032 +/- 0.007 L/year, which was not significantly different from that in patients taking ICS (- 0.027 +/- 0.010 L/year). Conclusion Pulmonary function decline is not greater in cough variant asthma than atopic cough and the normal population, and long-term ICS has no effect on the decline in cough variant asthma.