| Studies of the effects of exposure to electromagnetic fields emitted from mobile phones on volunteers |
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Topic Studies of the effects of exposure to electromagnetic fields emitted from mobile phones on volunteers Start 01.10.2003 End 31.03.2007 Project Management Berlin Free University Objective The objective of this project is to clarify whether high frequency electromagnetic fields emitted from mobile telephones influence brain activity. In experimental studies on man, there has been some indication that high frequency fields within approved exposure limits have a biological effect. However, there is no indication of increased health risk. During the experiments planned on 30 healthy volunteers, exposures will be similar to those received when using GSM or UMTS cell phone devices having the highest transmission power. In a double blind crossover design with randomised (assigned by a probability generator) exposure classification (including sham exposure), the possible influences of electrophysiological processes in the brain and cognitive ability will be studied. Target parameters during the day will be a) spontaneous waking EEG; b) evoked and event related potentials and c) cognitive function on various levels of complexity. In addition, sleep as a state of brain activity will be studied. Together with classic parameters used to describe nocturnal sleep, power spectral values should also be included in the analysis. Results At the beginning of the study, in 2004, a very extensive review of scientific literature on possible influences of high-frequency electromagnetic fields of mobile phones on brain activity, cognition, waking and sleep EEG and the sleep quality of humans was provided. This review was updated at the end of the study in 2007and is a part of the final report. Altogether, the available publications on the effects of electromagnetic fields of mobile phones show, as far as they could observe any changes of the examined parameters under exposure, only slight physiological effects, which, however, with the exception of increased power spectral values in the spindle frequency range of the NREM sleep could not be reproduced in other laboratories. Thirty healthy male volunteers at the age of 18 to 30 years took part in the study. Each volunteer was examined in 10 days and 10 nights. The first day and the first night served the adaptation, afterwards always three days and three nights were examined in a randomized double-blind cross-over design under the conditions sham, GSM-900 and UMTS. The volunteers were exposed using a portable antenna mounted on the head, by which the maximal permissible partial body exposure of 2 W/kg was reached, but not exceeded (IMST GmbH). During the days psycho-physiological investigations were performed and at the same time the EEG was recorded. Attention, sleepiness, reaction ability to visual and acoustic signals and the memory were examined. Waking-EEG at rest as well as the EEG in response to sensory cues and during cognitive brain performance was recorded. During the night the sleep-EEG was registered. The sleep-EEG was scored visually by experts according to the method by Rechtschaffen and Kales (1968) and additionally automatically using Somnolyzer. Furthermore, the power spectra and the sleep spindles were analyzed automatically as well. The sleep is divided into five stages: REM (rapid eye movement) corresponds to the dreaming phase, NREM1 (non-REM1) and NREM2 form together the light sleep, NREM3 and NREM4 the deep sleep. Altogether the visual and automatic evaluation of the sleep parameters showed under GSM 14 and under UMTS nine significantly changed parameters out of a total of 241. Twelve significant changes per exposure situation would be expected for purely statistic reasons. Not all of the changed parameters were independent from each other and they referred to a slight extension (few minutes) of the REM sleep with a simultaneous shortening of the sleep stages NREM1 and NREM2. The deep sleep as well as the total sleep duration remained unchanged, therefore, one can rate the observed effects as a slight physiological adaptation, but not as sleep-disturbing. Altogether 400 parameters of the power spectral values of the sleep-EEG, distributed over the various frequency ranges and sleep stages, were examined. 32 of them were significantly changed under GSM, and nine under UMTS, whereby in all cases there was an increase of the power spectral value under exposure. Twenty significant changes per exposure situation would be expected for statistic reasons. The changes showed up particularly in the awake condition and during light sleep at frequencies of about 20 Hz, in the deep sleep as well as in the REM sleep no significant changes were found. Publications reporting changes of the power spectra under GSM during REM sleep (Mann and Röschke, 1996), as well as during the NREM sleep, but in other frequency ranges than in the present study (Borbély et al. 1999; Huber et al. 2000, 2002; Loughran et al. 2005), could not be confirmed. Sleep spindles are sequences of sinusoidal waves in the frequency range of 12 - 14 Hz, occurring particularly in the sleep stage NREM2. Per exposure situation 810 parameters of the sleep spindles were automatically evaluated, 24 of them were significantly changed under GSM and 11 under UMTS. Forty significant differences would be expected in each exposure situation just per chance. The published data on the influence of a GSM exposure on sleep spindles (Borbély et al. 1999; Huber et al. 2000, 2002) could not be confirmed in the present study. The cognitive performance was examined using 8 different tests, which provided a total of 36 parameters. Under GSM 5 parameters (from 3 tests), under UMTS 2 parameters (from 2 tests), were significantly changed, respectively. Predominantly reaction times in response to different stimuli were affected in different directions (prolongation or shortening). After a correction for multiple tests none of these changes remained significant. Controversially, a continuous significant influence of the time of day on the results showed up, in the sense of a increased activation and wakefulness in the afternoon, accompanied by shortened reaction times and an improved cognitive performance. To some extent, an exercise effect might have contributed to the improvement in the afternoon. The temporal influences were clearly more pronounced than the most likely coincidentally arising influences of the exposure. This results are in agreement with data from scientific literature, where shortened reaction times were reported (Koivisto et al. 2000), but could not to be reproduced (Haarala et al. 2004). During the day tests the waking EEG as well as evoked and event-related potentials were registered. Altogether 361 parameters of the α-frequency band of the waking EEG were examined, 10 of them showed a significant influence of the GSM exposure and 5 a significant influence of the UMTS exposure. Eighteen significant results have to be expected in each case per chance. The increase of the power in the α -frequency band, reported in scientific literature several times (Curcio 2005, Vecchio 2007, Croft 2007), could not be confirmed in the presented study. However, the power in the α-frequency range of the EEG was continuously significantly higher in the afternoon than in the morning. An evaluation of the relationship between the power in the α-frequency range registered with eyes opened or closed allows conclusions on the wakefulness. It could be shown again, that not the exposure, but the day time affects the wakefulness, which was better in the afternoon. This finding is in accordance with the results of the cognition tests. Evoked and event-related potentials, occurring in response to sensory signals and in advance of a motion reaction, showed likewise only the influence of the day time, but no dependence on the exposure. This is in accordance with published data, showing a few significant changes due to an exposure to mobile phone signals, which could not be reproduced even within the same working group (Krause, 2007; Hamblin, 2006). The final report (3.397 KB) with an appendix (270 KB) can be downloaded as a PDF-file in German with English abstract. References
Conclusions Altogether the presented study could not confirm the results published so far on influences of the GSM of signal on sleep and cognition. For UMTS comparable publications are yet not available. The few significant effects described here point, as far as they are not coincidental, at most to a slight physiological adaptation, but not to a health impairment. No sleep-disturbing effects were found. During the day tests the influence of the day time was for all examined parameters considerably stronger than the effect of mobile phone exposure. |