Obesity and cardiac autonomic nerve activity in healthy children: Results of the toyama birth cohort study.

OBJECTIVES To determine the relationship between obesity and cardiac autonomic nerve activity in healthy children. METHODS 16 healthy male children comprising of 9 nonobese and 7 obese subjects (body mass index > 19.1 kg/m(2)) aged 8-9 years were selected. Electrocardiograms were measured for 10 min. under controlled ventilation (0.25 Hz) in the supine position. Consecutive 256-second RR interval data were transformed by the Fast Fourier Transform method into power spectral data. Very low frequency (VLF; 0.003-0.04 Hz), low frequency (LF; 0.04-0.15Hz), high frequency (HF; 0.15-0.40Hz), and total power (TP; 0.003-0.40Hz) were calculated and transformed into a natural logarithm (In). Normalized units (nu) were also calculated as follows: LFnu=LF/(TP-VLF)x100. HFnu=HF/(TP-VLF)x100. Low/high-frequency ratio (LHR) was calculated as LF divided by HF. Unpaired t test was performed to compare the 2 groups. RESULTS TP In and HFnu, reflecting cardiac parasympathetic nerve activity, in obese children were significantly lower than those in nonobese children. In contrast, LFnu and LHF, reflecting cardiac sympathetic nerve activity, in obese children were significantly higher than those in nonobese children. CONCLUSIONS These findings suggest that obese children have higher sympathetic nerve activity and lower parasympathetic nerve activity than nonobese children.