Occurrence of new-onset wheeze in a 3-year follow-up study of schoolchildren.

BACKGROUND: Different wheeze phenotypes have been identified, primarily in preschool children. OBJECTIVE: To explore the characteristics of children in primary school without a history of wheeze or asthma and the onset of wheeze during a 3-year follow-up period. METHODS: Students in grades 1 to 3 participated in a cross-sectional study in 2000 and again in 2003, creating a prospective cohort. Data were collected using questionnaires in both years. Children without a history of asthma or wheeze in or before 2000 were selected for this analysis (n = 212). Associations between baseline characteristics and an outcome of the onset of new wheeze were evaluated. RESULTS: Twenty-two children (10.4%) reported new wheeze by 2003. Significant associations were found between new-onset wheeze and body mass index (odds ratio OR], 1.33; 95% confidence interval CI], 1.10-1.62) and history of allergic disease (OR, 7.17; 95% CI, 2.48-20.72); significant inverse associations were found with farming exposures in the first year of life (OR, 0.17; 95% CI, 0.05-0.64) and with having a fireplace in the home (OR, 0.20; 95% CI, 0.05-0.83). After stratification by sex, the associations were typically stronger in girls than in boys. CONCLUSIONS: Allergic disease in childhood and early and current exposures affect the development of wheeze. These results support efforts to lead healthy lifestyles and direct continued research into wheeze phenotypes, especially by sex.