Prevalence of asthma and related symptoms in school-age children in São Paulo, Brazil--International Study of Asthma and Allergies in Children (ISAAC).

We studied the prevalence of asthma and related symptoms using a standard written questionnaire designed for the International Study of Asthma and Allergies in Children (ISAAC). The written questionnaire (questions 1-8 related to asthma) was applied to 3005 children aged 6-7 years and to 3008 children aged 13-14 years. The parents of the 6-7-year-old children answered the questionnaire, whereas the 13-14-year-old children answered the questionnaire themselves. Response rates were 72% in the 6-7-year-old group and 94% in the 13-14-year-old group. There was a slight predominance of females in the population studied (male:female ratio 0.94). In the group of the 6-7-year-old children, the prevalence of diagnosed asthma was 7.3% for boys and 4.9% for girls, and in the group of the 13-14-year-old children, the prevalence was 9.8% and 10.2% for boys and girls, respectively. Asthma severity was similar for both age groups, and wheezing following exercise was more frequent among the adolescents. In keeping with studies in other parts of the world, comparison between reported symptoms and diagnosed asthma revealed significantly lower frequency of diagnosed asthma, suggesting that in the population we have studied, asthma is underdiagnosed. Using a global cut-off score to define asthma, we found a significantly higher prevalence of asthma among 6-7-year-old boys, as compared to girls (23.8% vs. 20.4%), and no significant differences among adolescent boys and girls (22.5% and 21.9%, respectively).