Allergic sensitization associates differently to asthma, rhinitis and eczema during school ages

Background: Allergic sensitization (AS) is related to asthma, rhinitis and eczema. The association may however differ by disease and age. Aim: Investigate the relationship between AS and asthma, rhinitis and eczema at ages 7-8, 11-12 and 19 years. Methods: A cohort of schoolchildren within the Obstructive Lung disease in Northern Sweden (OLIN) Studies was examined at ages 7-8, 11-12 and 19y with questionnaires and skin-prick test (SPT) to airborne allergens. Participation was n=2148 (89%) at 7-8, n=2179 at 11-12 and n=1875 at 19y. Current asthma, rhinitis and eczema, respectively, was defined as a physician-diagnosis and either symptoms or treatment for the condition. Results: Prevalence of any positive SPT increased from 21% at 7-8, to 31% at 11-12 and 42% at 19y. AS to animals and pollen dominated, while AS to mites and moulds was uncommon. From 7-8 to 19y, the prevalence of current asthma was stable at 6-7%, as was eczema, 10-11%, while rhinitis increased from 6 to 13%. In multivariate analyses, AS was strongly related to rhinitis at all ages, increasing from OR 14 (95%CI 9.2-21) at 7-8y to OR 25 (95%CI 15-40) at 11-12y and OR 23 (95%CI 14-38) at 19y, with strongest associations to pollen AS. AS was related to asthma (OR range 4.4-6.6) without pattern by age, and in general, animal AS showed strongest association. AS showed weaker but significant association with eczema, and OR decreased by age (OR 2.7-1.9). AS to pollen and animal showed similar associations. Conclusion: Allergic sensitization was significantly associated with all outcomes at all ages. However, the strength of associations between allergic agent and asthma, rhinitis and eczema differed and developed differently by age.