High incidence and persistence of airborne allergen sensitization up to age 19 years

Abstract

Background

Longitudinal population-based studies about the natural history of allergic sensitization are rare. The aim was to study incidence and persistence of airborne allergen sensitization up to young adulthood, and risk factors for early and late onset of sensitization.

Methods

All children aged 7-8 years in two municipalities in Northern Sweden were invited to a parental questionnaire and skin prick tests (SPT) to ten airborne allergens, and 2,148 (88%) participated. The protocol was repeated at age 11-12 and 19 years, and 1,516 participated in all three examinations.

Results

Prevalence of any positive SPT increased from 20.6% at age 7-8y to 30.6% at 11-12y, and 42.1% at 19y. Animals were the primary sensitizers at age 7-8y, 16.3%, followed by pollen, 12.4%. Mite and mold sensitization was low. Mean annual incidence of any positive SPT varied between 2.8-3.4/100/year, decreased by age for animal and was stable for pollen. Sensitization before age 7-8y was independently associated with family history of allergy, OR 2.1(95%CI 1.6-2.8), urban living, OR 1.9(95%CI 1.2-2.9), and male sex, OR 1.3(95%CI 1.0-1.7), and negatively associated with birth order, OR 0.8(95%CI 0.7-1.0) and furry animals at home, OR 0.7(95%CI 0.7-0.9). Incidence after age 11-12y was associated only with family history of allergy. Multi-sensitization at age 19y was significantly associated with early age at sensitization. Remission of sensitization was uncommon.

Conclusion

The increasing prevalence of allergic sensitization by age was explained by high incidence and persistence. After age 11-12y the factors urban living, number of siblings and male sex lost their importance.

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