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We were surprised to read in the exhaustive and, some might say, exhausting review of gender differences in airway behaviour by Becklake and Kauffmann1 that the most common respiratory symptom—namely, cough—deserved only a single sentence and was then dismissed. In fact, the most dramatic gender difference in airway sensitivity is seen with the cough reflex. We studied 163 consecutive, healthy, non-smoking volunteers (90 women, mean age 32 years) with an inhalation cough challenge of five one-second inhalations of 10% citric acid delivered from a Mefar dosimeter. Women coughed over 50% more than men (mean total cough score 19.1 versus 12.0, p<0.001). This confirms several other observations in the literature with both acid2 and capsaicin3 4inhalation.
It could be argued that the smaller airways of women allow for greater deposition of the protussive agent, but this cannot explain the twofold difference between the sexes in the incidence of ACE inhibitor-induced cough.5
Unlike many of the observations quoted in their review, this gender difference in the cough reflex sensitivity has important clinical implications. In the Hull Cough Clinic we see twice as many women as men (64 versus 33 completed episodes last year). Other reported series have similar experiences.6 7
The fact that a review of 20 pages and 211 references did not comment on these observations is alarming. Surely the objective is to sift the literature, or is the policy now to publish gargantuan articles of the kind seen earlier last year on cytokines in asthma8 in order to enhance the journal's impact factor?
authors' reply In our review1-1 we used the term “airway behaviour” to refer to the dimensions, structure, and function of the airways and we examined the extent to which these accounted for the gender differences in obstructive airway disease. As Professor Morice and colleagues point out, cough as a variant of asthma should have been included, particularly since, as two of their references suggest,1-2 1-3 the lower threshold for cough in response to inhaling a tussive agent in women does not appear to be accounted for by methodological differences resulting from larger doses of the agent being delivered to their airways because of their smaller airway size.
We thank them for their references. Of particular interest to us was the observation that the cough was higher in premenopausal than in postmenopausal women.1-3 Our review would have predicted the opposite, based on the higher rates of asthma incidence in women during their reproductive years than in men, with reversal of these differences after the menopause. We attributed these changes to the hormonal effects on the airways of women. This paradox is one that invites further study.
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