Central Blood Pressure Regulation in Relation to Obesity in Youth

Abstract

Abstract Introduction Measures of central blood pressure (BP) are hypothesized to be positively associated with obesity status in youth. However, few studies have addressed this topic with a large sample size and wide range of BMI values. Methods A total of 310 participants (males/females =151/159) aged of 8 to 18 years old (mean±SD: 12.8±2.7 years) were recruited. Height (cm) and weight (kg) were measured using a wall-mounted stadiometer and an electric scale. Body mass index (BMI) was calculated (kg/m2) and obesity status was determined using age – and sex- derived BMI percentile (BMI%) with the following categories: normal weight (NW) represented as <85th BMI percentile; overweight/obesity (OW/OB) represented as between 85th to < 1.2 times the 95th BMI percentile); severe obesity (SO) represented as ≥ 1.2 times the 95th BMI percentile. Dual energy X-ray absorptiometry (DXA) was used to measure body composition. Brachial systolic (SBP) and diastolic (DBP) blood pressure was measured with an automated cuff. Central BP was obtained from SphygmoCor MM3 systems, which utilizes applanation tonometry to derive radial-aorta SBP (r-a SBP), radial-aorta DBP (r-a DBP), carotid-aorta SBP (c-a SBP), and carotid-aorta DBP (c-a DBP). Central BP measures were compared across obesity groups using ANCOVA with post-hoc Tukey HSD, adjusted for age, Tanner stage, sex, and race, with further adjustment of height for brachial BP. Unadjusted Pearson correlations examined the relationship between central BP measures with obesity (BMI, BMI%, body fat (%), visceral fat mass (kg)). Linear regression analyses examined the association between body fat (%) and visceral fat mass (kg) with brachial and central SBP and DBP after adjusting for age, Tanner stage, sex, and race, with height included for brachial BP. Results There were 120 NW, 89 OW/OB, and 99 SO participants. Body fat (%) was significantly different (p<0.001) among all obesity groups: NW (25.1±6.1 %), OW/OB (39.5±7.2 %), SO (48.0±4.9 %). Brachial SBP (bSBP), r-a SBP, and c-a SBP significantly increased (p<0.001 all) with increasing obesity status. BMI was significantly correlated (p<0.001 all) with bSBP (r=0.64), r-a SBP (r=0.57), and c-a SBP (r=0.52). BMI%, body fat (%), and visceral fat mass (kg) were also all significantly correlated to all brachial and Central BP measures. In multiple regression models, higher values of body fat (%) were significantly associated (all p<0.001) with higher brachial (r=0.66) and central SBP (r-a r=0.59) (c-a r=0.55) as well as brachial (r=0.44) and central DBP (r-a r=0.42) (c-a r=0.46). Higher values of visceral fat mass (kg) were significantly associated (all p<0.001) with higher brachial (r=0.61) and central SBP (r-a r=0.60) (c-a r=0.55) as well as brachial (r=0.39) and central DBP (r-a r=0.42) (c-a r=0.44). Older age was significantly associated with higher r-a SBP (r=0.59. p<0.001) and c-a SBP (r=0.55, p<0.01). Conclusion Central BP, regardless of measurement site, is highly associated with Obesity status (BMI, BMI%, body fat (%), and visceral fat mass (kg)) and hypertension status among youth.