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 (C₂) and those inducing five or more coughs (C₅) 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 C₂ values in smokers and nonsmokers were 1.26 ± 0.13 and 0.81 ± 0.08, respectively (p = 0.004). The mean log C₅ 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.