High prevalence of asthma in preschool children in Southern Brazil: a population-based study.

The prevalence of asthma is increasing in many countries. To measure asthma's prevalence, a sample of 981 children aged 4 years old belonging to a birth cohort from 1993 was studied in Pelotas, a city in southern Brazil. A standardized questionnaire on asthma was given to the children's mothers. Information was also collected on socioeconomic level, housing conditions, genetic factors, nutritional factors, and previous infectious diseases. Current asthma (asthma diagnosed by a doctor during previous 12 months) and current wheeze (presence of wheezing during previous 12 months) were the main outcomes. The prevalence of current asthma was 18.4%, and current wheeze was 21.1%. The data were analyzed by multiple Poisson regression, and the risk factors that remained significant for both "current asthma and current wheeze" were, respectively, nonwhite color (RR = 1.41 and RR = 1.36), low maternal schooling (RR = 1.75 and RR = 1.68 for 0-4 years), history of asthma or allergy in the family (RR = 1.66 and RR = 1.85), and history of rhinitis and eczema in the child (RR = 2.11 and RR = 1.72). Male sex (RR = 1.36) and bronchiolitis (RR = 1.46) were major risk factors only for "current asthma," while smoking in pregnancy (RR = 1.30) and low birth weight (RR = 1.45) were risk factors only for "current wheeze." These results highlight the importance of asthma as a public health problem due to its high prevalence, and support the need of intervention programs against preventable risk factors.