title: Segment-specific carotid intima-media thickness and cardiovascular risk factors in Koreans: the Healthy Twin Study.
abstract: BACKGROUND
  Increased carotid intima-media thickness is associated with higher cardiovascular disease risk. This study aimed to evaluate the contributions of cardiovascular risk factors and inheritance to segment-specific carotid intima-media thickness.
  
  
  METHODS
  Cross-sectional observational study.
  
  
  METHODS
  A total of 706 Korean adults was selected from the Healthy Twin Study. The intima-media thickness of common, carotid bifurcation, and internal carotid artery were measured using B-mode ultrasound. Behavioral and biological cardiovascular risk factors were measured. Quantitative genetic and linear mixed analyses were performed to examine inherited and environmental contributions to intima-media thickness variation.
  
  
  RESULTS
  Heritability of intima-media thickness was moderately high with estimates (95% confidence intervals) of 0.48 (0.37, 0.59), 0.38(0.27, 0.49), and 0.45(0.34, 0.55) for common, carotid bifurcation, and internal carotid artery, respectively. The additive genetic cross-trait correlations between the segments ranged between 0.43 and 0.75, suggesting a shared genetic influence on the three carotid segments. Additive inherited effects contributed 21% and 31% (common and internal carotid, respectively) to the total variance of the intima-media thickness, while measured cardiovascular risk factors accounted for 46% and 26% (common and internal carotid, respectively). The cardiovascular risk factors significantly associated with carotid intima-media thickness were as follows: in men, alcohol use (bifurcation); physical activity (common and internal); BMI (all segments); diabetes (bifurcation and internal); hypertension (internal); and HDL-cholesterol (common and bifurcation); and in women, smoking (bifurcation), hypertension (common), total and LDL cholesterol (bifurcation and internal), and hs-CRP (common and internal).
  
  
  CONCLUSIONS
  Individual cardiovascular risk factors were differentially associated with carotid intima-media thickness by segments and sex. Inherited effects made a heterogeneous contribution to intima-media thickness by segment. These findings may explain the differences in cardiovascular disease occurrence between men and women.
authors.affiliation: Department of Family Medicine, Busan Paik Hospital, Inje University College of Medicine, Pusan, Korea.
authors.forename: Kayoung
authors.initials: K
authors.lastname: Lee
authors.forename: Joohon
authors.initials: J
authors.lastname: Sung
authors.forename: Sang Cheol
authors.initials: SC
authors.lastname: Lee
authors.forename: Seung Woo
authors.initials: SW
authors.lastname: Park
authors.forename: Youn Sic
authors.initials: YS
authors.lastname: Kim
authors.forename: Joo Yeon
authors.initials: JY
authors.lastname: Lee
authors.forename: Shah
authors.initials: S
authors.lastname: Ebrahim
authors.forename: Yun-Mi
authors.initials: YM
authors.lastname: Song
mesh_terms: D000328:Adult; D002318:Cardiovascular Diseases / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000235:genetics; D017536:Carotid Artery, Common / Q000000981:diagnostic imaging*; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging*; D059168:Carotid Intima-Media Thickness; D003430:Cross-Sectional Studies; D004200:Diseases in Twins; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014427:Twins