Differences in incidence of reported asthma related to age in men and women - A retrospective analysis of the data of the European Respiratory HealthSurvey

Sex differences in asthma prevalence and morbidity, assessed with different methods in different populations, have raised several hypotheses about the different susceptibility to asthma in men and women. However, information on the incidence of asthma by age and sex is limited. The aim of this study was to estimate the age- and sex-specific incidence of asthma from birth t o 44 yr of age in men and women across several countries, and to evaluate t he main factors influencing asthma incidence in young adults. The data of t he European Community Respiratory Health Survey, an international, cross-se ctional, population-based survey, which were collected in 16 countries from 1991 to 1993 according to a common protocol, and which pertained to 18,659 subjects, were analyzed retrospectively, using the reported age of the fir st attack as the onset of asthma. During childhood, girls had a significant ly lower risk of developing asthma than did boys (relative risk [RR]: 0.74 and 0.56 in the 0- to 5-yr and 5- to IO-yr age classes, respectively). Arou nd puberty, the risk was almost equal in the two sexes (RR = 0.84; 95% conf idence interval [CI]: 0.65 to 1.10 in the 10 to 15-yr age class). After pub erty, the risk in women was always significantly higher than that in men (R R: 1.38 to 5.91). This pattern was consistent in all of the 16 countries st udied, and was not influenced by recall or cohort effects. When the effects of airway caliber and smoking were studied with a case-control design, the results showed that women's greater susceptibility to asthma in early adul thood was at least partly, explained by their smaller airway caliber (the O R decreased from 2.04 [95% CI: 1.32 to 3.15] to 1.47 [95% CI: 0.89 to 2.44] after controlling for height-adjusted FEV1); while smoking did not increas e the risk. This analysis strongly confirms that the incidence of asthma sh ows a sex reversal during puberty, and suggests that airway caliber, in add ition to hormonal factors, could play an important role in explaining the d ifferent patterns of asthma incidence in men and women.