title: Dental caries and allergic disorders in Japanese children: the Ryukyus Child Health Study.
abstract: BACKGROUND
  Dental caries is an infectious disease and is highly prevalent among children. In the etiology of allergic diseases, the hygiene hypothesis contends that infections might confer protection against the development of allergic diseases. The aim of this cross-sectional study was to investigate the association between dental caries and the prevalence of allergic disorders.
  
  
  METHODS
  Study subjects were 21,792 children 6 to 15 years of age in Okinawa, Japan. Outcomes were based on diagnostic criteria from the International Study of Asthma and Allergies in Childhood. Data on dental caries were obtained from school records. Children were classified as having dental caries if one or more teeth had decayed and/or had been filled. Adjustment was made for sex, age, region of residence, number of siblings, smoking in the household, paternal and maternal history of asthma, atopic eczema, or allergic rhinitis, and paternal and maternal educational level.
  
  
  RESULTS
  The prevalence of wheeze, asthma, atopic eczema, and allergic rhinoconjunctivitis in the previous 12 months was 10.8%, 7.6%, 6.8%, and 7.6%, respectively. In an overall analysis, no measurable relationship was found between dental caries and the prevalence of wheeze, asthma, atopic eczema, or allergic rhinoconjunctivitis. However, dental caries was significantly inversely associated with the prevalence of allergic rhinoconjunctivitis only among children with a positive parental allergic history: The adjusted odds ratio was 0.84 (95% confidence interval: 0.72, 0.99).
  
  
  CONCLUSIONS
  The present findings do not support the hypothesis that dental caries was protective against allergic diseases. However, a parental allergic history may affect the association between dental caries and allergic rhinoconjunctivitis.
authors.affiliation: Department of Public Health, Faculty of Medicine, Fukuoka University, Fukuoka, Japan. k-tanaka@fukuoka-u.ac.jp
authors.forename: Keiko
authors.initials: K
authors.lastname: Tanaka
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Miyake
authors.forename: Masashi
authors.initials: M
authors.lastname: Arakawa
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sasaki
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Ohya
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000453:epidemiology; D002648:Child; D003430:Cross-Sectional Studies; D003731:Dental Caries / Q000453:epidemiology*; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology*; D007564:Japan / Q000453:epidemiology; D008297:Male; D015995:Prevalence