Circulation Research in Astrobiology : Effect of Geomagnetic Disturbances on Heart Rate Variability

Recently, geomagnetic disturbances have been indicated as a remote cause of myocardial infarction or stroke. However, the mechanism of this effect remains unclear. We identified geomagnetic activities to be a cosmic synchronizer of biological clocks and investigated the effects of geomagnetic activities on heart rate variability (HRV). The effect of geomagnetic disturbances on HRV was longitudinally examined using 7-day successive records obtained by Holter ECG in 19 adult healthy subjects living in a subarctic area (Alta, Norway, 70 degrees N), where the biological effects of geomagnetic activities have been suggested to be stronger than in other areas. A geomagnetic record (one-minute interval between data acquisition) was obtained from the Auroral Observatory of the University of Tromso in Tromso, Norway (69 degrees N). HRV decreased in a dose-dependent fashion with geomagnetic disturbances. In the cross-spectral analysis, geomagnetic Pc6 pulsations observed on magnetically disturbed days were correlated with HRV for the 'very low frequency (VLF)' spectral power. The response of HRV to geomagnetic activities was influenced by the light/dark cycle. The power-law scaling of the power spectra (1/f fluctuation) became steeper on days with increased geomagnetic disturbance, and the alterations persisted for long periods after the geomagnetic storms. To evaluate whether an artificially generated magnetic field modeled on geomagnetic disturbances would similarly affect the HRV of subjects living in a subarctic area (Winnipeg, Canada, 50 degree N), three healthy volunteers (a Japanese student living in Winnipeg and two Canadians living in the same dormitory as the Japanese student; mean age, 29 years) underwent twelve 8-hour periods of exposure and sham exposure to the ultra low frequency magnetic fields (ULF-MFs; approximately 30 nT, 1.6 mHz) in a room shielded from extremely low frequency (ELF) and very low frequency (VLF) magnetic fields. The blood pressure and HRV of the subjects were monitored for 24 hours, including the 8-hour periods of exposure or sham exposure. Exposure to ULF-MFs influenced HRV, though individual or circadian variations were observed. These results suggest that concomitant longitudinal monitoring of geomagnetic activities and clinical data, especially HRV, may provide useful information for the design of adverse vascular events countermeasures