Cardiovascular risk factors significantly correlate with autonomic nervous system activity in children

Information is limited about the correlation between cardiovascular risk factors (CRFs) and autonomic nervous system (ANS) activity in children.

In all, 180 children aged 9 to 11 years were enrolled. Heart rate variability, obtained by 24-hour Holter recordings, was analyzed for ANS activity by measuring standard deviation of normal-to-normal RR intervals (SDNN), the standard deviation of the averaged normal-to-normal RR intervals, the root mean square of successive differences (RMSSD), low-frequency (LF), high-frequency (HF), and ratio of LF to HF. CRFs were defined as hypertension, dyslipidemia, obesity, and elevated fasting blood glucose. Children were subdivided into 4 levels: 0 (no CRF), 1 (1 CRF), 2 (2 CRFs), or 3 (3 or more CRFs). Altered ANS activity of each level was assessed. The correlation between CRF and ANS activity was analyzed by stepwise multiple regression.

With an increasing number of CRFs, there was a progressive elevation in blood pressure, obesity indices, most blood lipoprotein concentrations, and fasting blood glucose. Moreover, increase in the number of CRFs was associated with progressive reduction of SDNN, RMSSD, LF, and HF. Systolic blood pressure (SBP) correlated negatively with SDNN, RMSSD, LF, and HF. Obesity indices had a negative correlation with RMSSD and HF. As the number of CRFs increases, so does the extent of abnormal clustering of CRFs and changes in ANS activity.

Obesity and elevated SBP are associated with marked alterations in ANS activity, obesity with reduced vagal nerve activity, and elevated SBP with altered vagal and sympathetic nerve activity.