Background: Asthma is considered the most common chronic childhood disease. However, there have been few studies on the prevalence of asthma in Brazil. Objective: To assess the prevalence and severity of asthma symptoms in school-age children and adolescents living in the city of Duque de Caxias, located in the greater metropolitan area of Rio de Janeiro. Method: Cross-sectional transversal study using the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. The sample comprised students of 6, 7, 13 and 14 years of age. Results: One group of 2334 students between the ages of 6 and 7 and another composed of 4040 students between the ages of 13 and 14 were evaluated. The prevalence of wheezing within the last 12 months in the younger children was 27.7%, vs. 19% among the adolescents (p < 0.0001). There was a predominance of males in the 6-7 age group (29.9% vs. 25.6%; p = 0.01) and of females in the 13-14 age group (21.9% vs. 15.8%; p < 0.0001). The proportion of previously diagnosed cases of asthma was similar (approximately 10%) for both age brackets. Wheezing upon physical exertion was more prevalent among the adolescents (21.4% vs. 7.8%; p < 0.0001). Symptom severity was higher among female adolescents (severe asthma: 6.6% vs. 4.4%; p = 0.001), although no differences among genders were seen in the 6-7 age group. Conclusion: Asthma prevalence in Duque de Caxias is high, as it is in other Brazilian and Latin American cities. Values are higher in the 6-7 age group, in which symptoms were seen predominantly in males. Among the adolescents, the prevalence and severity of symptoms were higher in females, a recent observation that seems to be a new epidemiological trend of asthma.

Keywords: Key words: Asthma. Epidemiology. Severity of illness index. Cross-sectional studies.