title: Atopy risk factors at birth and in adulthood.
abstract: OBJECTIVE
  To study the association between atopy and variables such as weight, length, and socioeconomic level at birth and in young adulthood.
  
  
  METHODS
  A total of 2,063 subjects were investigated in a prospective birth cohort study of individuals born in Ribeirão Preto, Brazil, in 1978/1979, and examined at the age of 23-25 years. Skin prick tests (SPT) for eight common allergens in Brazil were performed. Subjects with a wheal reaction ≥ 3 mm to one or more of the eight allergens tested were considered to be atopic. We used the log-binomial model (generalized linear model) in order to assess the association between atopy and birth or adult variables.
  
  
  RESULTS
  The prevalence of positive SPT was 47.6%. Male gender was associated with an increased risk of atopy (relative risk [RR] = 1.18; 95% confidence interval [95%CI] 1.07-1.30). Low level of schooling was a protective factor against atopy, with a RR = 0.74; 95%CI 0.62-0.89. Living with a smoker in childhood was also associated with lower risk of atopy (RR = 0.87; 95%CI 0.79-0.96). Birth weight, length and order, maternal age, and intrauterine growth restriction were not associated with positive SPT.
  
  
  CONCLUSIONS
  This study showed that male gender was associated with an increased risk of atopy. Low socioeconomic status, assessed by low level of schooling, was a protective factor against atopy. These data agree with the hygiene hypothesis.
authors.affiliation: Departamento de Clínica Médica, Universidade de São Paulo (USP), Av. Bandeirantes 3900 – Monte Alegre, Ribeirão Preto, SP, Brazil.
authors.forename: Erica
authors.initials: E
authors.lastname: Ferraz
authors.forename: Clécia Aparecida
authors.initials: CA
authors.lastname: Garcia
authors.forename: Heloísa
authors.initials: H
authors.lastname: Bettiol
authors.forename: Roseane Durães
authors.initials: RD
authors.lastname: Caldeira
authors.forename: Viviane Cunha
authors.initials: VC
authors.lastname: Cardoso
authors.forename: Luiza Karla
authors.initials: LK
authors.lastname: Arruda
authors.forename: Marco Antônio
authors.initials: MA
authors.lastname: Barbieri
authors.forename: Elcio Oliveira
authors.initials: EO
authors.lastname: Vianna
mesh_terms: D000328:Adult; D000485:Allergens / Q000145:classification / Q000276:immunology; D001724:Birth Weight / Q000502:physiology*; D001827:Body Height / Q000502:physiology*; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D016014:Linear Models; D008297:Male; D036801:Parturition / Q000502:physiology*; D011446:Prospective Studies; D012307:Risk Factors; D012882:Skin Tests; D012959:Socioeconomic Factors; D055815:Young Adult
chemical_list: D000485:Allergens