Ki Chang Nam1, Ju Hyung Lee2, Hyung Wook Noh2, Eun Jong Cha3, Nam Hyun Kim2, 4, Deok Won Kim2, 4
1Korea Electrotechnology Reserch Institute, Ansan, Republic of Korea
2Graduate Program in Biomedical Engineering, Yonsie University, Seoul, Republic of Korea
3Department of Biomedical Engineering, Chungbuk National University, Cheongjoo, Republic of Korea
4Department of Medical Engineering, Yonsei University College of Medicine, Seoul, Republic of Korea
Summary of research published in Bioelectromagnetics, Volume 30, No. 8, pp.641-650.
Why is this research area important to Bioelectromagnetics?
With the rapidly increasing number of cellular phone users, the number of people with self-attributed electromagnetic hypersensitivity (EHS) who complain of various subjective symptoms, such as headache, insomnia, nervousness, distress, fatigue, and short-term memory loss, has increased as well. In a population based survey, the prevalence of EHS was reported to be 1.5% in Sweden, 3.2% in California, 4% in the UK, 5% in Switzerland, and 8-10% in Germany. EHS could not only deteriorate the quality of individual patients’ lives, but also cause an increase of social expenses for health care. Therefore, the objective of our research was to determine whether EHS results from actual physiological changes or psychological causes.
What was already done about this topic prior to this research?
For EHS related studies, three general methods have been utilized to investigate the origins of the EHS. The first is to measure the physiological variables such as heart rate, respiration rate or/and blood pressure etc. during sham and real exposures for the EHS or/and non-EHS group. The second is to survey those subjective symptoms during sham and real exposures for the EHS or/and non-EHS group. The third method is to determine perception accuracies during sham and real exposures for the EHS or/and non-EHS group. Most research has been carried out using one or two methods with GSM phones, but not with Code Division Multiple Access (CDMA) phones.
What did this work contribute to the subject?
We simultaneously investigated the physiological parameters, subjective symptoms, and EMF perception accuracy using CDMA phones for the EHS and non-EHS groups. We concluded that 300 mW exposures from CDMA phones for one half-hour did not have any effects on physiological variables such as the heart, respiration rate, or low frequency power/high frequency power (LFP/HFP), which was used as an index for the balance of autonomic nervous system in either group. It also did not produce any subjective symptoms in either group. As for EMF perception, there was no evidence that the EHS group’s perception of EMF was better than the non-EHS group. The possibility of a delayed exposure effect in the EMF perception was observed in the EHS group, but not in the non-EHS group.
We found two additional important findings in our study. While responding to questions regarding symptoms and EMF perception, 10 of the 37 subjects showed considerably varied skin conductance because of increased sweat secretion during sham exposure resulting from an excited sympathetic nervous system. Despite this, we still believe that it is a good parameter for investigating the autonomic nervous system if there are no such inquiries for subjective symptoms or EMF perception involved in the test.
Second, even though the experiments were performed during the day, drowsiness was observed in approximately half of all subjects because the subjects were in comfortable postures for more than an hour in a quiet room. If the examiner noticed a subject’s drowsiness, he made a noise to wake the subject up, resulting in sleep deprivation. We observed monotonically increased LFP/HFP at each exposure stage during sham exposure in both groups. Such a continuous increase is assumed to have been caused by sleep deprivation during the 64-min experiment. It has been reported that sleep deprivation could increase LFP and LFP/HFP. The usage of heart rate or HRV with unwanted drowsiness may falsely indicate the effects of RF radiation by mobile phones on the autonomic nervous system.