Genetic and environmental contributions to XXXX development in a twin population.

@entity1 @entity11557 @entity66 @entity439 @entity1028
BACKGROUND: The contribution of hereditary and environmental factors to the development of @entity1028 ( @entity1028 ) is still partly unknown. The aim of this study was to analyze the role of these factors in a large population-based sample of twins. METHODS: The Swedish Twin Registry, containing data on twins born in the country since 1886, was cross-linked with the Inpatient Registry, providing national coverage of discharge diagnoses coded according to the @entity66 ( @entity66 ). All twins with an infrarenal @entity11557 were identified. Concordance rates and tetrachoric correlations were calculated for monozygotic (MZ) and dizygotic (DZ) twins. Tetrachoric correlations were calculated assuming an underlying normal distribution of liability, with multiple factors contributing additively and a threshold value that discriminates between @entity11557 and no @entity11557 . Higher concordance rates and correlations of liability in MZ twins than in DZ twins suggest that genetic factors influence disease development. Structural equation modeling techniques, Mx-analyses, were used to estimate the contributions of genetic effects as well as shared and nonshared environmental factors for development of @entity11557 . RESULTS: There were 172,890 twins registered at the time of the study including 265 twins (81% @entity1 ; mean age 72 years; range, 48-94) with @entity11557 . There were 7 MZ and 5 DZ concordant pairs as well as 44 MZ and 197 DZ discordant pairs with @entity11557 . The probandwise concordance rates for MZ and DZ pairs were 24% and 4.8%, respectively. The tetrachoric correlations were 0.71 in MZ pairs and 0.31 in DZ pairs. The odds ratio (OR) was 71 (95% confidence interval [CI] 27-183) for MZ twins and 7.6 (95% CI 3.0-19) for DZ twins. In the structural equation models, genetic effects accounted for 70% (95% CI 0.33-0.83), shared environmental effects for 0% (95% CI 0-0.27), and nonshared environmental effects for 30% (95% CI 0.17-0.46) of the phenotypic variance among twins. CONCLUSION: These data provide robust epidemiologic evidence that heritability contributes to @entity439 formation. Concordances and correlations were higher in MZ compared with DZ twins, indicating genetic effects. There was a 24% probability that an MZ twin of a @entity1 with @entity11557 will have the disease. The twin of an MZ twin with @entity11557 had a risk of @entity11557 that was 71 times that of the MZ twin of a @entity1 without @entity11557 . A heritability of 70% of the total trait variance was estimated. The remaining variance was explained by nonshared environmental factors with no support for a role of shared environmental influences.
