Cough reflex sensitivity in cigarette smokers.

STUDY OBJECTIVES To evaluate cough reflex sensitivity in a population of young, healthy, male cigarette smokers. DESIGN Cross-sectional comparison. SETTING Academic medical center. PARTICIPANTS Twenty healthy, male current-smokers (mean [+/- SEM] age, 32.2 +/- 1.2 years). MEASUREMENTS Subjects underwent baseline spirometry followed by capsaicin cough challenge testing, which involved the inhalation of capsaicin in ascending, doubling concentrations until the concentrations inducing two or more coughs (C(2)) and those inducing five or more coughs (C(5)) were reached. The data were compared to those from a group of 50 healthy, male nonsmokers who had undergone identical cough challenge testing. RESULTS The two groups did not differ in terms of age or baseline pulmonary function. Cough sensitivity was significantly diminished in the current-smokers compared to control subjects. The mean (+/- SEM) log C(2) values in smokers and nonsmokers were 1.26 +/- 0.13 and 0.81 +/- 0.08, respectively (p = 0.004). The mean log C(5) values in smokers and nonsmokers were 2.03 +/- 0.10 and 1.20 +/- 0.08, respectively (p < 0.000001). CONCLUSIONS Cough reflex sensitivity is significantly diminished in young, healthy, male current-smokers compared to a similar population of nonsmokers. The mechanism of cough suppression in smokers remains speculative but may involve long-term tobacco smoke-induced desensitization of the cough receptors within the airway epithelium.