title: Season of birth and risk of atopic disease among children and adolescents.
abstract: BACKGROUND
  Season of birth (SOB) has been regarded as a risk factor for atopy. The aim of this study was to explore the relationship between season of birth (SOB) and later development of atopic disease in children and adolescents.
  
  
  METHODS
  A total of 1,007 randomly selected subjects, 7 to 17 years of age, who were living in urban Copenhagen, Denmark were studied. All participants were interviewed about respiratory symptoms and possible risk factors for atopic disease. Skin test reactivity, serum total immunoglobulin E (IgE), and airway responsiveness were measured using standard techniques.
  
  
  RESULTS
  The overall risk of atopy, as judged by skin test reactivity and serum total IgE, was the same regardless of SOB. On the contrary, asthma was more common in subjects born in the autumn compared with subjects born during the remaining part of the year (12.4% vs. 5.6%), OR = 2.40, 95% CI (1.56-3.94), p < 0.001. This was observed both for atopic asthma OR = 2.41, 95% CI (1.25-4.64), p = 0.007, non-atopic asthma, OR = 2.35, 95% CI (1.14-4.83), p = 0.02, and house dust mite (HDM) sensitive airway hyperresponsiveness, OR = 3.00, 95% CI (1.44-6.24), p = 0.002. Rhinitis and pollen allergy were not significantly related to SOB.
  
  
  CONCLUSIONS
  Atopy itself is independent of season of birth, whereas asthma is more prevalent among subjects born during the autumn. Regarding asthma, these results suggest that the first months of life enclose a period of particular vulnerability towards environmental risk factors, especially exposure to aeroallergens like HDM.
authors.affiliation: Department of Respiratory Medicine, Bispebjerg Hospital, Denmark. thomas@uknet.dk
authors.forename: Thomas Bøllingtoft
authors.initials: TB
authors.lastname: Knudsen
authors.forename: Simon Francis
authors.initials: SF
authors.lastname: Thomsen
authors.forename: Charlotte Suppli
authors.initials: CS
authors.lastname: Ulrik
authors.forename: Mogens
authors.initials: M
authors.lastname: Fenger
authors.forename: Steen
authors.initials: S
authors.lastname: Nepper-Christensen
authors.forename: Vibeke
authors.initials: V
authors.lastname: Backer
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000453:epidemiology; D001985:Bronchial Provocation Tests; D002648:Child; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000453:epidemiology*; D007073:Immunoglobulin E / Q000097:blood; D008297:Male; D012220:Rhinitis / Q000453:epidemiology; D012307:Risk Factors; D012621:Seasons; D012882:Skin Tests
chemical_list: D007073:Immunoglobulin E