title: Recurrent otitis media and tonsillitis: common disease predisposition.
abstract: OBJECTIVE
  To estimate the relative contribution of genetic and environmental effects to the association between recurrent otitis media and recurrent tonsillitis.
  
  
  METHODS
  Self-report questionnaire data from a population-based cohort of 9479 Norwegian twins born from 1967 to 1979. Recurrent otitis media and recurrent tonsillitis were main outcome measures. Structural equation modelling was used to fit alternative biometric models to the twin data and to estimate the relative contribution of genetic and environmental effects to the association between otitis media and tonsillitis.
  
  
  RESULTS
  The lifetime prevalence was 11.7% (95% CI: 11.0-12.3) for recurrent tonsillitis and 11.2% (95% CI 10.5-11.9) for recurrent otitis media. Tetrachoric correlations were greater in monozygotic than in dizygotic twins in both males and females. A model specifying additive genetic effects and individual environmental effects for otitis media and tonsillitis and non-additive genetic effects for tonsillitis yielded the best fit. There was no evidence for sex differences in the genetic source or magnitude of the genetic effects. There was a substantial overlap in genetic factors influencing variation in liability to otitis media and tonsillitis.
  
  
  CONCLUSIONS
  Common genetic factors contribute substantially to comorbidity between recurrent otitis media and recurrent tonsillitis.
authors.affiliation: Division of Epidemiology, Norwegian Institute of Public Health, Oslo, Norway. ellen.kvestad@fhi.no <ellen.kvestad@fhi.no>
authors.forename: Ellen
authors.initials: E
authors.lastname: Kvestad
authors.forename: Kari Jorunn
authors.initials: KJ
authors.lastname: Kvaerner
authors.forename: Espen
authors.initials: E
authors.lastname: Røysamb
authors.forename: Kristian
authors.initials: K
authors.lastname: Tambs
authors.forename: Jennifer Ruth
authors.initials: JR
authors.lastname: Harris
authors.forename: Per
authors.initials: P
authors.lastname: Magnus
mesh_terms: D004777:Environment; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D010033:Otitis Media / Q000150:complications* / Q000453:epidemiology / Q000235:genetics*; D015995:Prevalence; D012008:Recurrence; D011795:Surveys and Questionnaires; D014069:Tonsillitis / Q000150:complications* / Q000453:epidemiology / Q000235:genetics*