[Atopy among children and adolescents in Copenhagen]

Atopy is related to the presence of rhinitis and asthma, but our knowledge about its longitudinal predictors is limited.

Data from a 6-yr follow-up study of a population sample of children and adolescents (n = 408), aged 7 to 17 yr. at enrollment, were analysed to investigate the prevalence and predictors of atopy. Case history, including allergic diseases and smoking habits, was elicited by interview and questionnaire. Skin prick test reactivity to common allergens, total serum IgE, airway responsiveness, and pulmonary function were measured.

The point prevalence of atopy increased from the first to the second survey, 26% and 44%, respectively; 23% of the participants were atopic only at the second survey. Sensitisation to house dust mites (HDM), grass, dogs, cats, and birch pollen increased significantly in both the males and the females. However, no gender differences in the prevalence of positive reactions were found at the first survey, whereas atopy to grass and HDM was significantly more prevalent in males than in females at the second survey. Analysis of the data solely on participants who were non-atopic at the first survey showed that exposure to maternal smoking (OR 2.0, CI 1.3-3.1; p = 0.002), increased serum IgE (OR 1.7, CI 1.2-2.3; p = 0.001), new asthma (OR 1.6, CI 1.2-2.7; p = 0.03), and new rhinitis (OR 2.1, CI 1.2-3.6; p = 0.01) were associated with an increased risk of a positive skin prick test at the second survey.

This longitudinal population study showed an increase in the point prevalence of atopy in Danish children and adolescents; and, furthermore, that exposure to maternal smoking during childhood, increased serum IgE, and new symptoms of asthma or rhinitis were associated with an increased risk of developing sensitisation to common aeroallergens in late adolescence.