[Risk factors for the development of asthma in children and adolescents. Results of a longitudinal study].

To investigate risk factors for the development of asthma, a population sample of children and adolescents, aged 7 to 17 yrs at enrollment, were studied twice, with a six year interval; complete data was available for 408 subjects (199 males). Obtained case history was used to assess the presence of asthma; pulmonary function, skin prick test reactivity, total serum IgE and bronchial responsiveness to inhaled histamine (BHR) were measured using standard techniques. The 12-month period prevalence of asthma increased significantly from the first to the second examination in both males (p < 0.001) and females (p < 0.001), whereas the number of subjects with a positive histamine challenge test declined in both sexes. The prevalence of a positive skin prick test was higher at the second examination (26% and 44%, respectively, p < 0.001); the proportion of subjects with a positive skin reaction to house dust mite (HDMpos) increased from 14% to 26%. Confining the analysis to subjects without a history of asthma at the first examination showed that asymptomatic BHR (Odds Ratio [OR] 3.8 [95% Confidence Interval (CI) 2.5-5.1], p = 0.0002), HDMpos (OR 2.6 [CI 1.9-3.3], p = 0.005), a history of wheezy bronchitis before the age of two yrs (OR 3.8 [CI 2.4-5.2], p = 0.006) and a history of rhinitis and/or eczema (OR 2.8 [CI 1.7-3.9], p = 0.007) at first examination were associated with an increased risk for development of symptomatic asthma at some point between the two examinations. No significant relationship could be demonstrated between smoking (passive or active) and the risk for development of asthmatic symptoms. In conclusion, this longitudinal population study showed an increase in the 12-month period prevalence of asthma with sensitization to HDM and asymptomatic BHR as important risk factors for development of asthma.