Heritability of carotid intima-media thickness: a twin study.
OBJECTIVE
To estimate the heritability of carotid intima-media thickness (IMT), a surrogate marker for atherosclerosis, independent of traditional coronary risk factors.


RESULTS
We performed a classical twin study of carotid IMT using 98 middle-aged male twin pairs, 58 monozygotic (MZ) and 40 dizygotic (DZ) pairs, from the Vietnam Era Twin Registry. All twins were free of overt cardiovascular disease. Carotid IMT was measured by ultrasound. Bivariate and multivariate analyses were used to determine the association between traditional cardiovascular risk factors and carotid IMT. Intraclass correlation coefficients and genetic modeling techniques were used to determine the relative contributions of genes and environment to the variation in carotid IMT. In our sample, the mean of the maximum carotid IMT was 0.75+/-0.11. Age, systolic blood pressure and HDL were significantly associated with carotid IMT. The intraclass correlation coefficient for carotid IMT was larger in MZ (0.66; 95% confidence interval [CI], 0.62-0.69) than in DZ twins (0.37; 95% CI, 0.29-0.44), and the unadjusted heritability was 0.69 (95% CI, 0.54-0.79). After adjusting for traditional coronary risk factors, the heritability of carotid IMT was slightly reduced but still of considerable magnitude (0.59; 95% CI, 0.39-0.73).


CONCLUSIONS
Genetic factors have a substantial influence on the variation of carotid IMT. Most of this genetic effect occurs through pathways independent of traditional coronary risk factors.
Zhao
Jinying
J
Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30306, United States.
Cheema
Faiz A
FA
Bremner
J Douglas
JD
Goldberg
Jack
J
Su
Shaoyong
S
Snieder
Harold
H
Maisano
Carisa
C
Jones
Linda
L
Javed
Farhan
F
Murrah
Nancy
N
Le
Ngoc-Anh
NA
Vaccarino
Viola
V
D050197:Atherosclerosis / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000235:genetics*; D002339:Carotid Arteries / Q000000981:diagnostic imaging / Q000473:pathology*; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012042:Registries; D017539:Tunica Intima / Q000000981:diagnostic imaging / Q000473:pathology*; D017540:Tunica Media / Q000000981:diagnostic imaging / Q000473:pathology*; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D014463:Ultrasonography; D014481:United States / Q000453:epidemiology