Exposure to pulsed high-frequency electromagnetic field during waking affects human sleep EEG

Huber R, Graf T, Cote KA, Wittmann L, Gallmann E, Matter D, Schuderer J, Kuster N, Borbely AA, Achermann P

NeuroReport Volume 11, number 15, 3321-3325, 2000

The aim of the study was to investigate whether the electromagnetic field emitted by digital radiotelephone handsets affects brain physiology.

The main effect was the enhancement of the intensity of certain frequencies of the brainıs electrical signals (i.e. electroencephalogram, EEG) in the first 30 minutes of non-REM sleep.

The extensive use of mobile phones has given rise to public debate about possible adverse effects on human health. A recent report of the Independent Expert Group on Mobile Phones established by the British government summarized the relevant studies on the biological effects of electromagnetic fields (EMF). They proposed that a precautionary approach be adopted until more robust scientific information becomes available. In a previous study, the authors demonstrated that exposure to EMF during sleep reduced waking after sleep onset and affected the EEG in non-rapid eye movement (non-REM) sleep.

In this present study, the authors investigated the effect of exposure to pulsed high-frequency EMF during waking on subsequent sleep. Fields similar to those emitted by mobile communications equipment of GSM type (global system for mobile communication) were applied.

To simulate the real-life exposure conditions, the subjects were exposed on either side of the head. The EMF was directed to either the right or left side of the head for 30 min. The subsequent sleep episode was analyzed. As in a previous study, in which mechanical stimulation of the right hand had been shown to induce unilateral changes in the sleep EEG, the authors anticipated hemispheric differences.

Exposure to EMF affected neither the sleep stages, nor were significant effects of EMF exposure observed for subjective assessment of waking after sleep onset, sleep latency, and sleep quality.

The main effect of EMF exposure was the enhancement of the intensity of the brainıs electrical signals (EEG power density) in the frequency range of 9.750 - 11.25 Hz and in the 12.25 - 13.25 Hz in the first 30 minutes of non-REM sleep. This effect was also present when the left and right exposure were analyzed separately. The two sides of the brain were similarly affected after left and right exposure. A comparison within individuals showed that the spectral spindle peak frequency in the 10 - 15 Hz range was not shifted by left and right exposure. The REM sleep spectrum was not significantly affected.

In this study the authors have shown for the first time that exposure to EMF during waking affects the EEG during subsequent sleep. In the authorsı previous study, the EMF was directed towards the top of the head to expose both sides of the brain. In the present experiment, the field was aimed at one side or the other. Contrary to the authorsı expectation, the change in the brainıs electrical signal intensity was similar for both sides of the head.

The present results lend support to previous reports on effects of EMF on physiological and psychological variables. These include sleep and cognitive function as well as blood pressure and heart rate. However, the present study is unique in having confirmed previous results of an experiment performed under similar conditions on the effect on sleep. The other findings still need to be replicated or could not be reproduced.

This study demonstrates that a short exposure to an electromagnetic field similar to those emitted by mobile phones has an effect on brain physiology. Conclusions about possible adverse effects on human health are premature because the underlying mechanisms are unknown. Further studies are needed to determine the time course of the changes, to specify field strength - response relationships, and to define the critical field parameters (e.g. modulation, frequency).