title: Otitis media: genetic factors and sex differences.
abstract: Although genetic factors are recognised as major contributors to otitis media, the presence of sex differences in heritability needs clarification. The aim of this study was to estimate the relative contribution of genetic and environmental effects in otitis media liability with particular focus on sex differences. Data from a cohort of Norwegian twins born between 1967 and 1979 with repeated measures on recurrent childhood otitis media were analysed. Altogether the sample included 4247 twin pairs. The tetrachoric correlations for monozygotic twins were .71 and .65 for males and females respectively. In dizygotic twins the correlations were .35 and .25 for males and females, respectively, and was.34 in opposite sexed pairs. The contribution of genetic and environmental effects was analyzed using structural equation modeling. The best fitting model showed that additive genetic effects explained 72% and 61% of the variance in males and females, respectively. The remaining variance was attributed to individual environmental effects. A model specifying equal heritability estimates for males and females yielded an almost equivalent fit. We found substantial genetic effects for liability to otitis media. There is no evidence that different sets of genes influence liability in males and females, but there may be sex differences in the relative importance of genetic effects.
authors.affiliation: Division of Epidemiology, The Norwegian Institute of Public Health, Oslo, Norway. ellen.kvestad@fhi.no
authors.forename: Ellen
authors.initials: E
authors.lastname: Kvestad
authors.forename: Kari J
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 R
authors.initials: JR
authors.lastname: Harris
authors.forename: Per
authors.initials: P
authors.lastname: Magnus
mesh_terms: D015331:Cohort Studies; D004200:Diseases in Twins / Q000235:genetics*; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D009664:Norway / Q000453:epidemiology; D010033:Otitis Media / Q000453:epidemiology / Q000235:genetics*; D010641:Phenotype; D012008:Recurrence; D012737:Sex Factors; D014427:Twins / Q000235:genetics*; D014429:Twins, Dizygotic / Q000235:genetics; D014430:Twins, Monozygotic / Q000235:genetics