[Prevalence and severity of asthma among adolescents and their relationship with the body mass index].

OBJECTIVE To investigate the relationship between the increase of body mass index and the prevalence and severity of asthma in adolescents from Santa Maria, in southern Brazil, and surrounding regions. METHOD A cross-sectional, observational, population-based study was carried out with 4,010 schoolchildren aged 13 and 14 years, without any gender restrictions, who answered the written questionnaire of the International Study of Asthma and Allergies in Childhood (ISAAC) phase III. Body mass index was used (kg/m2) as recommended by the World Health Organization for the assessment of nutritional status: below the fifth percentile (underweight), at or above the fifth percentile and below the 85th percentile (normal weight), at or above the 85th percentile and below the 95th percentile (overweight), and at or above the 95th percentile (obesity). The relationship between body mass index and the prevalence and severity of asthma was analyzed using the chi-square test for trend (statistical significance: p < or = 0.05). RESULTS There was a significant statistical association between the increase in body mass index and the prevalence of "wheezing ever" (p = 0.036), and "wheezing with exercise" (p = 0.008). When stratified by sex, there was a positive association just for "wheezing ever" (p = 0.028) for boys and "wheezing with exercise" (p = 0.03) for girls. CONCLUSION The increase in body mass index was associated with the increase in the prevalence of wheezing ever, but not with the increase in the prevalence and severity of asthma among adolescents.