Cardiac autonomic function and its association with cardiometabolic disease risk factors in Black South African children

Objective:This study evaluated the associations between cardiac autonomic nervous system (ANS) activity andcardiometabolic disease (CMD) risk factors among black South African children.Design:The participants included 34 black South African children (11.85 ± 0.89 y). CMD risk factors includedwaist circumference (WC), hip circumference (HC), body mass index z-score (BMI z-score), blood pressure (SBP,DBP), total cholesterol (TC), high density lipoprotein cholesterol (HDL), low density lipoprotein cholesterol(LDL), fasting glucose (FG), fasting insulin (FINS), and vessel stiffness index (SI). Heart rate variability was usedto quantify cardiac ANS activity.Results:lnRMSSD, pNN50 and lnSD1 were inversely associated with FINS (r=−0.33,p= 0.05;r=−0.36,p= 0.03;r=−0.41,p= 0.01), WC (r=−0.45,p= 0.01;r=−0.39,p= 0.02; r =−0.45,p= 0.01), and HC(r =−0.41,p= 0.01; r =−0.36,p= 0.03;r=−0.43,p= 0.01). HDL was positively associated withlnRMSSD (r= 0.37;p= 0.03) and lnSD1 (r = 0.37;p= 0.03) while, LDL was negatively associated with HF(r =−0.41;p= 0.01). Regression analysis identified WC as the primary predictor for parasympathetic mod-ulation in time domain (lnRMSSD: r2 = 0.21,p= 0.01; pNN50: r2 = 0.18,p= 0.01) and non-linear domain(lnSD1: r2 = 0.21,p= 0.01).Conclusion:Elevated resting parasympathetic activity in children is associated with lower CMD risk factors andan elevation in the protective HDL.