Cross-Sectional Study of Arterial Stiffness in Adolescents with Down Syndrome

Objectives: To test whether youth with Down syndrome have aortic stiffness indices, as measured by pulse wave velocity (PWV), that differ from youth without Down syndrome and to compare reference-based age-adjusted (age-PWV-Z) and height-adjusted (Ht-PWV-Z) in youth with and without Down syndrome. Study design: Cross-sectional study of PWV in 129 adolescents with Down syndrome and 97 youth of comparable age, sex, race/ethnicity, and body mass index (BMI). PWV, age-PWV-Z, and Ht-PWV-Z were compared. Regression models were developed to test for associations with PWV. Results: Youth with Down syndrome and controls were comparable in BMI-Z (1.4 [−1.5 to 2.8] vs 1.2 [−2.0 to 2.8], P = .57) but not Ht-Z (−2.3 [−4.7 to 0.8] vs 0.4 [−2.0 to 2.6], P < .0001). PWV (m/s, 5.0 [3.1-7.9] vs 5.0 [3.6-8.0], P = .5) and mean arterial pressure (MAP, mm Hg) (78 [61-102] vs 74 [64-97], P = .09) were not different between groups. In adjusted analyses confined to Down syndrome, PWV was associated only with BMI, but not age, black race, or MAP (R² = 0.11). In contrast, BMI, age, black race, and MAP were all positively associated with and better explained PWV in controls (R² = 0.50). PWV was not associated with height in youth with or without Down syndrome. Although age-PWV-Z was not different in Down syndrome (−0.36 [−2.93 to 3.49]) vs −0.15 [−2.32 to 3.22]), Ht-PWV-Z was greater in Down syndrome (0.32 [−2.28 to 4.07] vs −0.08 [−2.64 to 2.64], P = .002), and Ht-PWV-Z was greater than age-PWV-Z in Down syndrome (P < .0001). Conclusions: The lack of relationship of PWV, an independent predictor of adult cardiovascular events, with its traditional determinants including MAP suggests Down syndrome−specific phenomena may alter such relationships in this population. In youth with Down syndrome, Ht-adjusted PWV may overestimate aortic stiffness. Trial Registration: Clinicaltrials.gov: NCT01821300.