Sleep of Poor and Good Nappers Under the Afternoon Exposure to Very Weak Electromagnetic Fields

It was hypothesized that human sleep is sensitive to the fields emitted by natural sources, such as the earth’s magnetic fields and the sun’s magnetic activity. However, the experiments aimed on testing the response of sleep to such fields are scarce. A possibility of beneficial response of sleep in the afternoon to exposure to low-level (0.004 μT) electromagnetic fields of very low frequencies (from 1 Hz to 8 Hz) was examined in three experiments. In the 1st experiment, a significant increase in amount of stage 2 sleep was observed under exposure to 1 Hz/0.004 μT electromagnetic field during the 50-min napping attempts of 23 healthy volunteers. In the 2nd experiment, a significant increase in amount of stage 3 (slow wave) sleep and power density in delta frequency range of the electroencephalographic spectrum was found under exposure to the 2 Hz/0.004 μT electromagnetic field during the napping attempts of 14 good nappers, while sleep of 13 poor nappers under such an exposure was not improved in the 3rd experiment. Therefore, although the effects of very weak 1 Hz–2 Hz electromagnetic fields might be beneficial for sleep intensity (for instance, they can prolong deep sleep stages), it is unlikely that they can additionally help in treating difficulties of falling asleep. These results should be considered exploratory and their replication in larger samples is necessary. We, nevertheless, hypothesized the underlying mechanism: very weak 1 Hz–2 Hz electromagnetic fields can modulate the subconscious neural processes by promoting further synchronization of activity of neuronal networks involved in the generation of slow waves during deep sleep stages.