Heritability of arterial stiffness and carotid intima-media thickness: an Italian twin study

Summary Background and aims Carotid intima-media thickness (IMT) and arterial stiffness parameters, including aortic augmentation index (AIx) and pulse wave velocity (PWV), are independent predictors of stroke and cardiovascular disease. Genetic effects on these traits were never explored in a Mediterranean country. The present study aims to quantify the contribution of genes, environment and age to carotid IMT and aortic Aix and PWV. Methods and results The twin design was used. A total of 348 adult twins from the Italian Twin Register underwent measurements of carotid IMT and aortic PWV and AIx in three university hospitals located in Rome, Padua and Perugia. Carotid IMT was measured by B-mode ultrasound, aortic PWV and AIx by Arteriograph. Genetic modelling was performed to decompose total variance of traits into genetic, shared and unshared environmental and age components. For each phenotype, the best-fitting model included additive genetic, unshared environmental and age effects. For IMT, heritability was 0.32 (95% confidence interval (CI): 0.25–0.38), unshared environmental component was 0.25 (0.18–0.32) and age contribution was 0.44 (0.39–0.49). For AIx and PWV, heritabilities were 0.42 (0.29–0.55) and 0.49 (0.35–0.62), unshared environmental components were 0.31 (0.22–0.44) and 0.37 (0.26–0.51) and age contributions were 0.27 (0.16–0.39) and 0.14 (0.06–0.24), respectively. Conclusion This study shows substantial genetic and unshared environmental influences on carotid intima-media thickness and arterial stiffness and confirms the relevant role of age in the aetiology of these traits. Further support is provided for prevention and health promotion strategies based on modifiable factors.