Atopy in Danish children and adolescents: results from a longitudinal population study

Background and objective: Atopy is an objectively measurable trait related to the presence of rhinitis and asthma, but our knowledge about its longitu dinal predictors is limited. Data from a 6-year follow-up study of a popula tion sample of children and adolescents (n = 408), aged 7 to 17 years at en rollment, were analyzed to investigate the prevalence and predictors of ato py. Methods: Case history, including allergic diseases and smoking habits, was obtained by interview and questionnaire. Skin prick test reactivity to comm on allergens, total serum IgE, airway responsiveness, and pulmonary functio n were measured using standard techniques. Results: The point prevalence of atopy increased from the first to the seco nd survey, 26% and 44%, respectively; 23% of the participants had a positiv e skin prick test only at the second survey. Sensitization to house dust mi te (HDM) (P < .001), grass (P < .001), dog (P < .001), cat (P < .001), and birch (P = .02) increased significantly in both males and females. No gende r differences in the prevalence of positive reactions were found at the fir st survey, whereas atopy to grass (P = .01) and HDM (P = .02) were more pre valent in males than in females at the second survey. Confining the analysi s to participants who were found to be non-atopic at the first survey showe d that exposure to maternal smoking (OR 2, CI 1.3 to 3.1; P = .002), increa sed serum IgE (OR 1.7, CI 1.2 to 2.3; P = .001), new asthma (OR 1.6, CI 1.2 to 2.7; P = .03), and new rhinitis (OR 2.1, CI 1.2 to 3.6; P = .01), but n ot active smoking, were associated with an increased risk for the presence of a positive skin prick test at the second survey. Conclusions: This longitudinal population study showed an increase in the p oint prevalence of atopy in Danish children and adolescents; and, furthermo re, that exposure to maternal smoking during childhood, increased serum IgE , and new symptoms of asthma or rhinitis were associated with an increased risk for developing sensitization to common aeroallergens in late adolescen ce.