Associations of sex, age and adiposity in endothelium-independent dilation in children

Objective: To examine the association of age, sex, and obesity status on endothelial-independent dilation (EID) among children and adolescents. Study design: This study examined 264 children (143 males) between 8 to 18 years old (mean ± SD: Age = 14.3 ± 2.7 years). Endothelial-independent dilation was assessed via ultrasound imaging of the brachial artery following administration of 0.3 milligrams of sublingual nitroglycerin. A one-way analysis of variance with Bonferroni post hoc comparisons assessed sex-differences in percent peak EID dilation (EID%-peak) and EID area under the curve (EID%-AUC), while analysis of covariance (ANCOVA) adjusted for race, age, body mass index percentile (BMI-percentile), and brachial artery diameter. Multiple linear regression evaluated the association of sex, age, BMI-percentile, percent body fat (%BF), and brachial artery diameter on EID. Results: Prior to adjustment, EID%-peak was significantly higher among females than males (mean ± SE: 26.9 ± 0.5% versus 22.9 ± 0.6%, p < 0.001, respectively); similar findings for EID%-AUC (4214% ± 105%•s versus 3398% ± 97%•s, p < 0.001) were observed. After adjusting for covariates, EID%-AUC remained consistent (p = 0.03) while EID%-peak was not significantly different between sexes (p = 0.21). EID%-peak was significantly higher among normal weight compared to obese participants (p = 0.04), while no differences were observed between obesity status after adjustment for brachial artery diameter (p = 0.64). Both unadjusted (p = 0.16) and adjusted EID%-AUC (p = 0.24) was not significantly different between obesity status. BMI-percentile was not associated with EID%-peak (p = 0.76) or EID%-AUC (p = 0.30). Additionally, %BF was not associated with EID%-peak (p = 0.56) or EID%-AUC (p = 0.15). After adjusting for brachial artery diameter, BMI-percentile, and age, males had lower EID%-AUC (p = 0.03) and lower but not significant EID%-peak (p = 0.21). Significance: Vascular smooth muscle function was significantly lower among male children and adolescents, which is suggestive that impaired EID and increased cardiovascular disease risk among males may begin in childhood. Interestingly, obesity status and BMI-percentile was not associated with EID in children and adolescents after adjusting for brachial artery diameter.