[Geomagnetic field effects on circadian variability of cardiac rhythm].

To study the effect of geomagnetic field (GMF) on circadian rhythm of the heart the author has examined 23 healthy children aged 5-16 years (mean age 12 +/- 4.8). All the examinees have undergone 24-h Holter monitoring with assessment of circadian fluctuations n cardiac rhythm variability (CRV). The data obtained on the parameters Mean, SDNN, SDNN = i, SDANN = i, rMSSD and pNN50 were compared to circadian fluctuations of 3-h indices GMF Ap-index in the test day with estimation of paired correlation index (r). Positive and negative relations between CRV and GMF changes were found in 6 and 8 children, respectively. Groups of GMF-sensitive and GMF-negative children were formed. At 10-year follow-up 3 of 7 GMF-sensitive and 6 of 9 GMF-resistant children developed nonspecific diseases. It is suggested that GMF may have a synchronizing effect on cardiac circadian rhythm. The response of cardiac rhythm to fluctuations of GMF is thought an individual chronotype of the body. GMF-resistant group is characterized by self-regulation of cardiac rhythm which determines reduced availability of exogenic synchronizing effects of GMF.