GENETIC-BASIS OF VARIATION IN CAROTID-ARTERY WALL THICKNESS

Background and Purpose Other than the documented associations of risk factors and carotid artery wall thickness, the genetic basis of variat ion in carotid artery intimal-medial thickness (IMT) is unknown. The p urpose of this study was to examine the extent to which variation in c ommon carotid artery (CCA) IMT and internal carotid artery (ICA) IMT a re under genetic control. Methods The sibship data used for this analy sis were part of an epidemiological survey in Mexico City. The CCA and ICA analyses were based on 46 and 44 sibships of various sizes, respe ctively. The CCA and ICA IMTs were measured with carotid ultrasonograp hy. Using a robust variance decomposition method, we performed genetic analyses of CCA IMT and ICA IMT measurements with models incorporatin g several cardiovascular risk factors (eg, lipids, diabetes, blood pre ssure, and smoking) as covariates. Results After accounting for the ef fects of covariates, we detected high heritabilities for CCA IMT (h(2) = 0.92 +/- 0.05, P = .001) and ICA IMT (h(2) = 0.86 +/- 0.13, P = .02 9). Genes accounted for 66.0% of the total variation in CCA IMT, where as 27.7% of variation was attributable to covariates. For ICA IMT, gen es explained a high proportion (74.9%) of total phenotypic variation. The covariates accounted for 11.5% of variation in ICA IMT. Conclusion s Our results suggest that substantial proportions of phenotypic varia nce in CCA IMT and ICA IMT are attributable to shared genetic factors.