Determinants of Intima-Media Thickness in the Young: The ALSPAC Study.

OBJECTIVES: This study characterized the determinants of carotid intima-media thickness (cIMT) in a large (n > 4,000) longitudinal cohort of healthy young people age 9 to 21 years. BACKGROUND: Greater cIMT is commonly used in the young as a marker of subclinical atherosclerosis, but its evolution at this age is still poorly understood. METHODS: Associations between cardiovascular risk factors and cIMT were investigated in both longitudinal (ages 9 to 17 years) and cross-sectional (ages 17 and 21 years) analyses, with the latter also related to other measures of carotid structure and stress. Additional use of ultra-high frequency ultrasound in the radial artery at age 21 years allowed investigation of the distinct layers (i.e., intima or media) that may underlie observed differences. RESULTS: Fat-free mass (FFM) and systolic blood pressure were the only modifiable risk factors positively associated with cIMT (e.g., mean difference in cIMT per 1-SD increase in FFM at age 17: 0.007 mm: 95% confidence interval [CI]: 0.004 to 0.010; p < 0.001), whereas fat mass was negatively associated with cIMT (difference: -0.0032; 95% CI: 0.004 to -0.001; p = 0.001). Similar results were obtained when investigating cumulative exposure to these factors throughout adolescence. An increase in cIMT maintained circumferential wall stress in the face of increased mean arterial pressure when increases in body mass were attributable to increased FFM, but not fat mass. Risk factor-associated differences in the radial artery occurred in the media alone, and there was little evidence of a relationship between intimal thickness and any risk factor. CONCLUSIONS: Subtle changes in cIMT in the young may predominantly involve the media and represent physiological adaptations as opposed to subclinical atherosclerosis. Other vascular measures may be more appropriate for the identification of arterial disease before adulthood.

Childhood Fat and Lean Mass: Differing Relations to Vascular Structure and Function at Age 8 to 9 Years

Objective- Childhood body mass index (BMI) has been related to vascular structure and function. However, little is known about the differing contributions of fat and lean mass to this relationship. Our objectives were to relate the fat and lean mass (bone excluded) components of BMI (fat mass index and lean mass index; mass [kg]/height [m]2) to vascular measures in prepubertal children. Approach and Results- In the UK Southampton Women's Survey mother-offspring cohort, 983 children had dual x-ray absorptiometry and vascular measurements at 8 to 9 years. Using linear regression analyses, we found that most vascular measures were related to BMI, but fat and lean mass contributed differently. Systolic blood pressure was positively associated with both fat mass index (ß=0.91 [95% CI, 0.52-1.30] mm Hg) and lean mass index (ß=2.16 [95% CI, 1.47-2.85] mm Hg), whereas pulse rate was positively associated with fat mass index (ß=0.93 [95% CI, 0.48-1.38] b/min) but negatively associated with lean mass index (ß=-1.79 [95% CI, -2.59 to -0.99] b/min). The positive relation between BMI and carotid intima-media thickness was mainly due to a positive association with lean mass index (ß=0.013 [95% CI, 0.008-0.019] mm). Carotid-femoral pulse wave velocity, but not carotid-radial pulse wave velocity, was positively associated with fat mass index (ß=0.06 [95% CI, 0.03-0.09] m/s). For systolic blood pressure, carotid-femoral pulse wave velocity and reactive hyperemia significant interactions indicated that the association with fat mass depended on the amount of lean mass. Conclusions- In prepubertal children, differences in vascular structure and function in relation to BMI probably represent combinations of adverse effects of fat mass, adaptive effects of body size, and relatively protective effects of lean mass.

Ethnic differences in carotid intima-media thickness between UK children of black African-Caribbean and white European origin.

BACKGROUND AND PURPOSE: UK black African-Caribbean adults have higher risks of stroke than white Europeans and have been shown to have increased carotid intima-media thickness (cIMT). We examined whether corresponding ethnic differences in cIMT were apparent in childhood and, if so, whether these could be explained by ethnic differences in cardiovascular risk markers. METHODS: We conducted a 2-stage survey of 939 children (208 white European, 240 black African-Caribbean, 258 South Asian, 63 other Asian, 170 other ethnicity), who had a cardiovascular risk assessment and measurements of cIMT at mean ages of 9.8 and 10.8 years, respectively. RESULTS: Black African-Caribbean children had a higher cIMT than white Europeans (mean difference, 0.014 mm; 95% CI, 0.008-0.021 mm; P<0.0001). cIMT levels in South Asian and other Asian children were however similar to those of white Europeans. Among all children, cIMT was positively associated with age, systolic and diastolic blood pressure and inversely with combined skinfold thickness and serum triglyceride. Mean triglyceride was lower among black African-Caribbeans than white Europeans; blood pressure and skinfold thickness did not differ appreciably. However, adjustment for these risk factors had little effect on the cIMT difference between black African-Caribbeans and white Europeans. CONCLUSIONS: UK black African-Caribbean children have higher cIMT levels in childhood; the difference is not explained by conventional cardiovascular risk markers. There may be important opportunities for early cardiovascular prevention, particularly in black African-Caribbean children.