Effect of age and sex on carotid intima-media thickness, elasticity and brachial endothelial function in healthy adults: The Cardiovascular Risk in Young Finns Study

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Abstract
The objective was to produce reference values and to analyse the associations of age and sex with carotid intima-media thickness (IMT), carotid compliance (CAC), and brachial flow-mediated dilatation (FMD) in young healthy adults. We measured IMT, CAC, and FMD with ultrasound in 2265 subjects aged 24–39 years. The mean values (mean ± SD) in men and women were 0.592 ± 0.10 vs. 0.572 ± 0.08 mm (P < 0.0001) for IMT, 2.00 ± 0.66 vs. 2.31 ± 0.77%/10 mmHg (P < 0.0001) for CAC, and 6.95 ± 4.00 vs. 8.83 ± 4.56% (P < 0.0001) for FMD. The sex differences in IMT [95% confidence interval (CI) for sex difference −0.013 to 0.004 mm, P = 0.37] and CAC (−0.01 to 0.18%/10 mmHg, P = 0.09) became non-significant after adjustments with risk factors and carotid diameter. In FMD, the sex difference was unaltered after adjustments for risk factors, but was reversed after adjustment with brachial diameter (95% CI 0.18–1.32%, P < 0.01). With aging, IMT increased 5.7 ± 0.4 µm/year and CAC decreased 0.042 ± 0.003%/10 mmHg/year. The association of age with IMT and CAC was slightly attenuated (12 and 22%, respectively) after adjustments with risk factors, but remained significant (both P < 0.0001). Aging was not significantly related to brachial FMD (P = 0.16). Reference values produced in the present study can be utilized in the cardiovascular risk stratification among young people. Sex differences in the markers of subclinical atherosclerosis were mostly explained by differences in risk factors and vessel size. This emphasizes the importance of risk factor control in the prevention of atherosclerosis in young adults.