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 micro g/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.