Prevalence of allergic rhinitis among adolescents from Distrito Federal, Brazil: comparison between ISAAC phases I and III

To determine the prevalence of allergic rhinitis in a random group of schoolchildren aged 13 to 14 years in Brasilia, Brazil, to evaluate tendencies over 6 years and to compare prevalence rates among different socioeconomic groups. Two cross-sectional studies were undertaken 6 years apart, using the ISAAC (phases I and III) written questionnaire. Thirty-nine schools were chosen at random from eight administrative regions in Brasilia, and were classified into three groups according to the socioeconomic conditions of the population. A total of 3,009 questionnaires were collected. Of these 53.5% related to female children and 80% to students from public schools. Prevalence rates for diagnosed rhinitis, recent rhinitis and allergic rhinitis were 20, 29.3 and 12.2%, respectively. Rhinitis was more prevalent in private schools than in public ones (17.8 versus 14.1%) and sufferers were predominantly female. Prevalence rates were also higher among populations with higher socioeconomic status (23.5 versus 12.2%). Comparison with the 1996 data revealed significant increases in the prevalence of diagnosed rhinitis (12.7 versus 20%, p = 0.001). These increases were observed at all socioeconomic levels. A large number of 13 and 14-year-old children resident in the Distrito Federal exhibit symptoms indicative of rhinitis and the majority of them have allergic rhinitis. Over a six-year period the prevalence of allergic rhinitis increased significantly, predominantly affecting females and with greater prevalence among students at private school and from families with higher socioeconomic status.