Recurrent otitis media and tonsillitis:: common disease predisposition

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 mates 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. Conclusion: Common genetic factors contribute substantially to comorbidity between recurrent otitis media and recurrent tonsillitis. (C) 2006 Elsevier Ireland Ltd. All rights reserved.