Sastre A, Graham C, Cook M R
Midwest Research Institute, 425 Volker Boulevard, Kansas City, MO 64110, USA.
Clin Neurophysiol. 2000 Nov;111(11):1942-8. doi: 10.1016/s1388-2457(00)00438-7.
Heart rate variability (HRV) is a noninvasive indicator of sympathetic and vagal cardiovascular control known to be tightly correlated with sleep stages. Recent studies indicate that HRV in humans is altered by nocturnal exposure to power-frequency (60 Hz) magnetic fields. Given the central origin of autonomic cardiac control, we determined if field exposure in the beta(1) EEG/MEG frequency range was a more effective stimulus for HRV alteration than 60 Hz fields, and explored the mechanisms involved.
Healthy young men were exposed (n=9) overnight to an intermittent magnetic field (16 Hz, 28.3 microTesla, microT), or sham exposed (n=9), under blind test conditions in a laboratory exposure facility.
Field exposure was associated (P<0.05) with reduced power in the low band of the HRV frequency spectrum, and with decreases in mean heart rate. Analysis of the timing of the R waves surrounding each on-off transition of the intermittent field revealed no evidence for a direct effect on the cardiac pacemaker.
Magnetic field exposure in the EEG/MEG beta(1) frequency range alters HRV via a CNS effect. Phase-resetting experiments rule out a direct effect on the cardiac pacemaker. Biophysical calculations of the intensity of the electric fields induced in brain versus heart under the present exposure conditions are also consistent with and support a central rather than a peripheral site of action.
心率变异性（HRV）是交感神经和迷走神经对心血管控制的一种非侵入性指标，已知其与睡眠阶段密切相关。最近的研究表明，夜间暴露于工频（60Hz）磁场会改变人类的HRV。鉴于自主心脏控制的中枢起源，我们确定了β（1）脑电/脑磁图频率范围内的磁场暴露是否比60Hz磁场更有效地刺激HRV改变，并探讨了其中涉及的机制。
在实验室暴露设施的盲测条件下，9名健康年轻男性夜间暴露于间歇磁场（16Hz，28.3微特斯拉，μT），或进行假暴露（9名）。
磁场暴露与HRV频谱低频带功率降低（P<0.05）以及平均心率降低有关。对间歇磁场每次开关转换周围R波的时间分析显示，没有证据表明对心脏起搏器有直接影响。
脑电/脑磁图β（1）频率范围内的磁场暴露通过中枢神经系统效应改变HRV。相位重置实验排除了对心脏起搏器的直接影响。在当前暴露条件下，大脑和心脏中感应电场强度的生物物理计算也与中枢而非外周作用部位一致并支持这一观点。
