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. 2009 Aug;124(2):357-63, 63.e1-15.
doi: 10.1016/j.jaci.2009.05.011. Epub 2009 Jul 3.

Major increase in allergic sensitization in schoolchildren from 1996 to 2006 in northern Sweden

Eva Rönmark  1 , Anders Bjerg, Matthew Perzanowski, Thomas Platts-Mills, Bo Lundbäck
Affiliations

Major increase in allergic sensitization in schoolchildren from 1996 to 2006 in northern Sweden

Eva Rönmark et al. J Allergy Clin Immunol. 2009 Aug.

Abstract

Background: Time trends for allergic sensitization are poorly known.

Objective: To compare the trends in prevalence of allergic sensitization and associated risk factors in children.

Methods: Two cohorts of children (age 7-8 years) were invited for skin prick tests (SPTs) 10 years apart, 1996 and 2006. The participation rates were 2148 (88%) and 1700 (90%), respectively. The methods were identical, and 10 common airborne allergens were used. An expanded International Study of Allergy and Asthma in Children questionnaire about symptoms and possible risk factors for allergic conditions was completed by the parents.

Results: The prevalence of any positive SPT increased from 21% in 1996 to 30% in 2006 (P < .001). The pattern of sensitization remained similar, and sensitization to cat was most common both years, 13% and 19%, respectively. Sensitization to mites and mold was uncommon in both surveys. A family history of allergy was a significant risk factor for a positive SPT both years (odds ratio, 1.7). Factors that in 1996 had a protective effect, such as rural living and having several siblings, had lost this effect in 2006. The prevalence of most risk factors remained similar, but respiratory infections and smoking among parents decreased significantly. During the same period, there was no significant increase in the prevalence of current wheeze (11.9% to 12.4%, P = .636) or symptoms of rhinitis or eczema.

Conclusion: The prevalence of allergic sensitization increased significantly from 1996 to 2006, whereas no increase in clinical symptoms was found. The parallel decrease in parental smoking and respiratory infections indicate a different influence of environmental factors on allergic sensitization and clinical symptoms, respectively.

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Conflict of interest statement

Conflict of interest: No author has any conflict of interest to declare.

Figures

Figure 1
Figure 1. Increase in allergic sensitization from 1996 to 2006 expressed as odds ratios
Footnote: Analysed by multiple logistic regression analyses including the variables sex, family history of allergy, number of siblings, rural living, living at a farm, and living within 200 m from a heavy traffic road as covariates.
Figure 2
Figure 2. Number of positive tests among sensitized children in 1996 and 2006
Footnote: Differences between number of positive tests in 1996 and 2006 calculated by One-Way ANOVA.
Figure 3
Figure 3. International trends in allergic sensitization in children
See this image and copyright information in PMC

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