ORIGINAL ARTICLE Gender differences in prevalence, diagnosis and incidence of allergic and non-allergic asthma: a population-based cohort Be ´ne ´dicte Leynaert, 1,2,3 Jordi Sunyer, 4,5,6,7 Raquel Garcia-Esteban, 4,5,7 Cecilie Svanes, 8,9 Deborah Jarvis, 10 Isa Cerveri, 11 Julia Dratva, 12,13 Thorarinn Gislason, 14 Joachim Heinrich, 15 Christer Janson, 16 Nino Kuenzli, 12,13 Roberto de Marco, 17 Ernst Omenaas, 8,18 Chantal Raherison, 19 Francisco Go ´mez Real, 8,20 Matthias Wjst, 21,22 Elisabeth Zemp, 12,13 Mahmoud Zureik, 1,2 Peter G J Burney, 10 Josep M Anto, 4,5,6,7 Franc ¸oise Neukirch 1,2 ABSTRACT Background Although women with severe non-allergic asthma may represent a substantial proportion of adults with asthma in clinical practice, gender differences in the incidence of allergic and non-allergic asthma have been little investigated in the general population. Methods Gender differences in asthma prevalence, reported diagnosis and incidence were investigated in 9091 men and women randomly selected from the general population and followed up after 8e10 years as part of the European Community Respiratory Health Survey. The protocol included assessment of bronchial responsiveness, IgE specific to four common allergens and skin tests to nine allergens. Results Asthma was 20% more frequent in women than in men over the age of 35 years. Possible under- diagnosis of asthma appeared to be particularly frequent among non-atopic individuals, but was as frequent in women as in men. The follow-up of subjects without asthma at baseline showed a higher incidence of asthma in women than in men (HR 1.94; 95% CI 1.40 to 2.68), which was not explained by differences in smoking, obesity or lung function. More than 60% of women and 30% of men with new-onset asthma were non-atopic. The incidence of non-allergic asthma was higher in women than in men throughout all the reproductive years (HR 3.51; 95% CI 2.21 to 5.58), whereas no gender difference was observed for the incidence of allergic asthma. Conclusions This study shows that female sex is an independent risk factor for non-allergic asthma, and stresses the need for more careful assessment of possible non-allergic asthma in clinical practice, in men and women. INTRODUCTION The prevalence of asthma shows a sex reversal around puberty from a higher risk in boys early in life to a higher risk in girls after adolescence. 1e6 This pattern has raised several hypotheses about the susceptibility to asthma of men and women, such as an effect of sex hormones, airway calibre, obesity, differences in exposure or diagnosis. 1e6 Further studies are needed to appraise how much these determinants could explain the higher risk of asthma in women. Data are lacking on whether women remain at increased risk of asthma throughout all the reproductive years, and few studies have investigated the possibility of a differ- ential diagnosis. 2e8 Furthermore, most studies are not of a prospective nature that allows separating new-onset asthma from persistent asthma or relapse. In addition, new-onset of non-allergic asthma appears to be relatively frequent in adult- hood. 9 Clinical studies suggest that non-allergic (or ‘intrinsic’) asthma may be more severe and difficult to control than allergic asthma, and that women might be at increased risk of non-allergic asthma. 10e14 However, most of our knowledge on non-allergic asthma comes from clinical studies which often include patients with more severe asthma, and little is known on non-allergic asthma in the general population. 14 Key messages What is the key question? < Are women really at increased risk of asthma, and what could explain this difference? What is the bottom line? < Women were found to be at increased risk of developing non-allergic asthma (no difference was found for allergic asthma), and this increased risk was not explained by differences in diagnosis, lung function (as a surrogate of airway calibre), obesity or smoking. Why read on? < Our data provide evidence that non-allergic asthma is still poorly recognised in men and women, and that women are at increased risk of developing non-allergic asthma compared with men. We suggest that sex hormones or other biological markers that significantly differ between men and women (such as adipocytes) may be involved in the development of non- allergic asthma. < Additional materials are published online only. To view these files please visit the journal online (http://thorax.bmj. com/content/early/recent). For numbered affiliations see end of article. Correspondence to Be ´ne ´dicte Leynaert, INSERM Unite ´ 700, Epide ´miologie e Faculte ´ de Me ´decine X, Bichat, 16 Rue Henri Huchard, Paris 75018, France; benedicte.leynaert@inserm.fr Received 17 October 2011 Accepted 12 January 2012 Leynaert B, Sunyer J, Garcia-Esteban R, et al. Thorax (2012). doi:10.1136/thoraxjnl-2011-201249 1 of 7 Epidemiology Thorax Online First, published on February 14, 2012 as 10.1136/thoraxjnl-2011-201249 Copyright Article author (or their employer) 2012. Produced by BMJ Publishing Group Ltd (& BTS) under licence. group.bmj.com on October 13, 2017 - Published by http://thorax.bmj.com/ Downloaded from