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Home > Vascular Annual Meeting^® > SS36. Genetic and Environmental Contributions...

SS36. Genetic and Environmental Contributions to Abdominal Aortic Aneurysm Development in a Twin Population

Carl Magnus Wahlgren, Patrik Magnusson, Emma Larsson, Rebecka Hultgren, Jesper Swedenborg
Karolinska Institute, Stockholm, Sweden

OBJECTIVES: The contribution of hereditary and environmental factors to development of abdominal aortic aneurysms (AAA) is still unclear. 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 1895, was cross-linked with the Inpatient Registry, providing national coverage of discharge diagnoses coded according to the International Classification of Diseases (ICD). All twins with an infrarenal AAA were identified. Concordance rates and tetrachoric correlations were calculated for monozygotic (MZ) and dizygotic (DZ) twins. Tetrachoric correlations were calculated for two normally distributed phenotypic variables that are both expressed as a dichotomy and reflect the similarity of twin pairs. Higher concordance rates and correlations of liability in MZ twins than in DZ twins suggest that genetic factors influence disease development. Structural equation modelling techniques, Mx-analyses, were used to estimate the contributions of genetic effects as well as shared and non-shared environmental factors for development of AAA.

RESULTS: There were 172890 twins registered at the time of the study including 266 twins (81% men; mean age 72 years, range 48-94) with AAA. There were 7 MZ and 5 DZ concordant pairs as wells 44 MZ and 197 DZ discordant pairs with AAA. 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. 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 non-shared environmental effects for 30% (95% CI: 0.17-0.46) of the phenotypic variance among twins.

CONCLUSIONS: In the largest AAA twin study to date, we could provide robust epidemiological evidence that heritability contributes to aneurysm formation. Concordances and correlations were higher in MZ compared with DZ twins, indicating genetic effects. A heritability of 70% of the total trait variance was estimated. The remaining variance was explained by non-shared environmental factors with no support for a role of shared environmental influences.

AUTHOR DISCLOSURES: C. Wahlgren, None; P. Magnusson, None; E. Larsson, None; R. Hultgren, None; J. Swedenborg, None.