The influence of gender on cough reflex sensitivity

Background: The more common occurrence in women of cough due to angiotensin-converting enzyme inhibitors raises the possibility of gender- related differences in the sensitivity of the cough reflex. Of two recent studies that evaluated cough response to inhaled capsaicin in normal subjects, one demonstrated heightened sensitivity of the cough reflex in women compared with men, while the other revealed no gender-related differences. To further investigate this question, we reviewed our experience with cough challenge testing in normal volunteers. Study objective: To compare cough reflex sensitivity in healthy adult female and male subjects. Design: Retrospective data analysis. Setting: Academic medical center. Participants: One hundred healthy volunteers (50 male, 50 female). Interventions: Subjects inhaled capsaicin in ascending, doubling concentrations until the concentration inducing five or more coughs (C₅) was reached. In addition, the concentration inducing two or more coughs (C₂; cough threshold) was measured. Results: Mean log Cs was significantly lower in women than in men: 1.02±0.00 (SEM) μM vs 1.41±0.08 μM, respectively (p=0.002). Log Ca (cough threshold) was also significantly lower in female subjects: 0.534±0.068 μM vs 0.870±+0.065 μM in male subjects (p=0.00058). Conclusion: Healthy women have a more sensitive cough reflex than do healthy men. The reasons for this significant gender difference remain to be elucidated, but may involve a heightened sensitivity, in women, of the sensory receptors within the respiratory tract that mediate cough.