Relationships between heart rate variability, vascular function, and adiposity in children.

OBJECTIVE: To examine the relationships and interactions between cardiovascular autonomic nervous system (cANS) function, adiposity, and vascular function in children of varying levels of adiposity.
METHODS: Participants were children (19 M, 17 F, age = 11.5 +/- 0.1 years) who had cANS function assessed via heart rate variability (HRV) methods during resting conditions. Vascular function was assessed with brachial artery flow-mediated dilation (FMD) and nitroglycerin-induced dilation. Spectral power of HRV was calculated for high frequency normalized units (HFnu; measure of PSNS activity) and low frequency:high frequency ratio (LF:HF; overall sympathovagal balance). A blood sample was drawn for measurement of fasting insulin, glucose, lipids, and C-reactive protein (CRP). Results were reported as mean +/- SEM.
RESULTS: FMD peak dilation was positively related to HFnu (r = 0.48, P = 0.01) and negatively related to LF:HF (r = -0.51, P = 0.01) indicating that reduced parasympathetic activity and states of dysfunctional sympathovagal balance were associated with decreased vascular function. After adjustment for confounding factors (insulin, CRP, age) and fat mass, the relationships between these measures of cANS and vascular function remained moderately strong and significant. DISCUSSION: These data indicate a relationship between cANS and vascular function that is independent of fat mass, inflammation (CRP), and fasting insulin in children of varying levels of adiposity. These relationships and the mechanisms by which they exist require further study to allow for the identification of appropriate therapies for children with high levels of adiposity given the likelihood of them having concomitant cANS and vascular dysfunction.