title: 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 (SPTs) to ten airborne allergens, and 2148 (88%) participated. The protocol was repeated at age 11-12 and 19 years, and 1516 participated in all three examinations.
  
  
  RESULTS
  Prevalence of any positive SPT increased from 20.6% at age 7-8 years to 30.6% at 11-12 years, and 42.1% at 19 years. Animals were the primary sensitizers at age 7-8 years, 16.3%, followed by pollen, 12.4%. Mite and mold sensitization was low. Mean annual incidence of any positive SPT varied between 2.8 and 3.4/100 per year, decreased by age for animal, and was stable for pollen. Sensitization before age 7-8 years 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 11-12 years was associated only with family history of allergy. Multisensitization at age 19 years was significantly associated with early age at sensitization. Remission of sensitization was uncommon.
  
  
  CONCLUSIONS
  The increasing prevalence of allergic sensitization by age was explained by high incidence and persistence. After age 11-12 years, the factors urban living, number of siblings, and male sex lost their importance.
authors.affiliation: Department of Public Health and Clinical Medicine, Division of Occupational and Environmental Medicine, The OLIN Unit, Umeå University, Umeå, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Rönmark
authors.affiliation: Department of Public Health and Clinical Medicine, Division of Occupational and Environmental Medicine, The OLIN Unit, Umeå University, Umeå, Sweden.|Division of Medicine, The OLIN Unit, Umeå University, Umeå, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Warm
authors.affiliation: Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Bjerg
authors.affiliation: Department of Public Health and Clinical Medicine, Division of Occupational and Environmental Medicine, The OLIN Unit, Umeå University, Umeå, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Backman
authors.affiliation: Department of Public Health and Clinical Medicine, Division of Occupational and Environmental Medicine, The OLIN Unit, Umeå University, Umeå, Sweden.|Department of Health Sciences, Division of Nursing, Luleå University of Technology, Luleå, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Hedman
authors.affiliation: Krefting Research Centre, Institute of Medicine, University of Gothenburg, Gothenburg, Sweden.
authors.forename: B
authors.initials: B
authors.lastname: Lundbäck
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000485:Allergens / Q000276:immunology*; D000818:Animals; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology*; D007114:Immunization; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D052638:Particulate Matter / Q000009:adverse effects*; D011058:Pollen; D011159:Population Surveillance; D015995:Prevalence; D012882:Skin Tests; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult
chemical_list: D000485:Allergens; D052638:Particulate Matter
keywords: allergic sensitization; epidemiology; longitudinal study; prevalence; risk factors