title: Development and comorbidity of eczema, asthma and rhinitis to age 12: data from the BAMSE birth cohort.
abstract: BACKGROUND
  Allergy-related diseases are a public health issue, but knowledge on development and comorbidity among children is scarce. The aim was to study the development of eczema, asthma and rhinitis in relation to sex and parental allergy, in a population-based cohort, during childhood.
  
  
  METHODS
  At 1, 2, 4, 8 and 12 years, parental questionnaires were used to obtain data on allergy-related diseases. Complete data for all five follow-up occasions were available from 2916 children. Odds ratios for the risk of any allergy-related disease in relation to heredity and sex were calculated using generalized estimating equations.
  
  
  RESULTS
  At 12 years, 58% of the children had had eczema, asthma and/or rhinitis at some time. Disease turnover was high for all three diseases throughout the study. Comorbidity increased with age, and at 12 years, 7.5% of all the children were affected by at least two allergy-related diseases. Parental allergy was associated with increased comorbidity and more persistent disease and increased the risk of having any allergy-related disease (adjusted OR 1.76; 95% CI 1.57-1.97) up to 12 years. Male sex was associated with an increased risk throughout childhood. Boys and girls did not differ in disease persistence, and for comorbidity, the differences were minor.
  
  
  CONCLUSIONS
  Allergy-related diseases may affect a majority of children. Eczema, asthma and rhinitis develop dynamically throughout childhood, and allergic comorbidity is common. These findings indicate that allergy-related diseases should be neither seen nor studied as isolated entities.
authors.affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.natalia.ballardini@ki.se
authors.forename: N
authors.initials: N
authors.lastname: Ballardini
authors.forename: I
authors.initials: I
authors.lastname: Kull
authors.forename: T
authors.initials: T
authors.lastname: Lind
authors.forename: E
authors.initials: E
authors.lastname: Hallner
authors.forename: C
authors.initials: C
authors.lastname: Almqvist
authors.forename: E
authors.initials: E
authors.lastname: Ostblom
authors.forename: E
authors.initials: E
authors.lastname: Melén
authors.forename: G
authors.initials: G
authors.lastname: Pershagen
authors.forename: G
authors.initials: G
authors.lastname: Lilja
authors.forename: A
authors.initials: A
authors.lastname: Bergström
authors.forename: M
authors.initials: M
authors.lastname: Wickman
mesh_terms: D001249:Asthma / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D015897:Comorbidity; D004485:Eczema / Q000453:epidemiology*; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007223:Infant; D008297:Male; D010290:Parents; D015995:Prevalence; D012220:Rhinitis / Q000453:epidemiology*; D012737:Sex Factors; D011795:Surveys and Questionnaires