Vagal baroreflex sensitivity (BRS) is a measure of short term blood pressure (BP)
regulation through alterations in heart rate. Low BRS reflects impaired autonomic system
regulation and has been found to be a surrogate marker for cardiovascular health. In
particular, it has found to be associated with the pathogenesis of adult hypertension.
However, only limited information exists as to the negative consequences of childhood
BP on baroreflex function. The objective of this study was to investigate BRS in children
with 2 different BP profiles while controlling for the effects of age, maturation, sex, and
body composition. A preliminary subsample of 11-14 year-old children from the HBEAT
(Heart Behavioural Environmental Assessment Team) Study was selected. The children
were divided into 2 BP groups; high BP (HBP; 2:95tl1 percentile, n=21) and normal BP
(NBP; <90th percentile, n=85). Following an initial 15 minutes of supine rest, 5 minutes of
continuous beat-to-beat BP (Finapres) and RR interval (RRI) were recorded (standard
ECG). Spectral indices were computed using Fast Fourier Transform and transfer
function analysis was used to compute BRS. High frequency (HF) and low frequency
(LF) power spectral areas were set to 0.15-0.4 Hz and 0.04-0.15 Hz, respectively. Body
composition was measured using body mass index. After adjusting for body composition,
maturation, age and sex ANCOV A results were as follows; LF and HF BRS, LF and HF
RRI, and RRI total power were lower in the HBP versus NBP participants (p<0.05). As
well, LF IHF SBP ratio was significantly higher in the HBP compared to the NBP group
(p<0.05). The regression coefficients (unstandardized B) indicated that in changing
groups (NBP to HBP) LF and HF BRS decreases by 4.04 and 6.18 ms/mmHg,
respectively. Thus, as BP increases, BRS decreases. These data suggest that changes in
autonomic activity occur in children who have HBP, regardless of age, sex, maturation,
and body composition. Thus, despite their young age and relatively short amount of time
having high BP compared with adults, these children are already demonstrating poor BP
regulation and reduced cardiovagal activity. Given that childhood BP is associated with
hypertension in adulthood, there is a growing concern in regards to the current
cardiovascular health of our children and future adults