Magnetic fields can be divided into geomagnetic field and electromagnetic field. There is scientific literature investigating the effects of both types of magnetic fields on sleep. Research in geomagnetism and sleep indicate that under the influence of a stronger geomagnetic field, humans are less likely to have bizarre dreams. This is related to melatonin secretion [1]. Another study produced a sealed metal chamber which blocks any geomagnetic influence on the human body. They found that without the influence of geomagnetism, brain waves had a tendency to reduce in amplitude, which means it was harder to enter the deep sleep phase. Also, there was a trend for increased body movements [2]. These observations suggest that geomagnetic field can improve sleep quality.

       On the other hand, research comparing personnel working at substations who were exposed to electromagnetic fields (50-60 Hz, 1 V/m-199 KV/m, 0.1 mG-20 G) and a control group shows that 28% of the group exposed to electromagnetic fields were diagnosed with poor health and 61% were diagnosed with sleep disorders. On the other hand, the control group only had 4.5% of people with poor sleep quality, and all were in good health condition. Although the data shows that exposure to electromagnetic fields negatively affected sleep quality and health condition, there was no significant relationship between the levels of electromagnetic field received and sleep quality or general health [3].

       There was another magnetic field and sleep study focused on women (sleep initiation and maintenance disorder, SIAMD), which found that 29.5% of participants had difficulty falling asleep (difficulty initiating sleep, DIS), 38.17% of participants had difficulty staying asleep (difficulty maintaining sleep, DMS), and 26.02% of participants woke up too early (early morning awakening, EMA). Among these three categories, the DIS and DMS conditions were significantly related to exposure to 2 mG or greater magnetic fields [4]. Other basic laboratory experiments found that exposure to magnetic fields resulted in a significant decrease of 16-29 minutes of total sleeping time and a 3-7% decrease in sleep efficiency [5,6].

       However, some experimental results indicate that being exposed to 60 Hz, 0.5-1.0 μT of magnetic field did not have any influence on sleep. This result may differ from the results of basic laboratory experiments because of different dosages of magnetic fields used (4-60 Hz, 0.5-28.3 μT), environmental factors or differences in statistical methods. Furthermore, in a study of exposing to the field from a 132,230,400 kilovolts high-voltage substation, although the experimental group had poorer sleep quality compared to the control group, there was still no significant difference. Therefore, the relationship between electromagnetic field and sleep still requires a more comprehensive and long term investigation to show more definite results.

NSD=No significant difference