Study type: Medical/biological study (experimental study)

Sleep EEG alterations: effects of pulsed magnetic fields versus pulse-modulated radio frequency electromagnetic fields. med./bio.

Published in: J Sleep Res 2012; 21 (6): 620-629

Aim of study (acc. to author)

The aim of the study was to test if a signal without significant harmonics above 20 Hz is sufficient to influence the EEG. In addition (part 2), the authors wanted to investigate whether applying a magnetic field with the same pulse sequence as applied in the pulse modulated radiofrequency exposure would result in similar changes in the EEG.

Background/further details

Part 2 was an attempt to test the demodulation hypothesis, i.e. that the effects are induced by the demodulated radiofrequency signal (corresponding to the low frequency envelope of the transmitted signal) via an electrically non-linear structure inside the human brain. Demodulation occurring in the brain has been proposed as one possible mechanism for the effects of pulse modulated radiofrequency electromagnetic fields.
25 young healthy men were exposed/sham exposed at weekly intervals to three different conditions for 30 min before sleep.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 900 MHz
Modulation type: pulsed
Exposure duration: continuous for 30 min
  • SAR: 2 W/kg (peak spatial average of head tissue)
Exposure 2: 2 Hz
Exposure duration: continuous for 30 min

Exposure 1

Main characteristics
Frequency 900 MHz
Type
Exposure duration continuous for 30 min
Modulation
Modulation type pulsed
Repetition frequency 2.08 Hz
Additional info

Pulsed signals had a basic modulation frequency of 2 Hz and a peak-to-average ratio of 4 in pulse amplitude. In order to reduce the higher harmonics the pulse structures were smoothened by applying a Gaussian low-pass filter (-3 dB at 20 Hz), reducing the spectral power above 20 Hz by more than a factor of 10 and by approx. 10 000 at 50 Hz.

Exposure setup
Exposure source
Distance between measurement device and exposure object 115 mm
Setup patch antenna 42 mm vertically above ear canal, 115 mm from left side of head (unilateral exposure)
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 2 W/kg - - - peak spatial average of head tissue

Exposure 2

Main characteristics
Frequency 2 Hz
Type
Waveform
Exposure duration continuous for 30 min
Exposure setup
Exposure source
Setup rectangular shaped coils (33 x 39 cm, 2 x 23 windings) on each side of the head separated by 25.7 ± 0.5 cm, depending on the participant's anatomy
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0.176 mT cf. remarks calculated - whole-brain time and spatial average
magnetic flux density 0.7 mT peak value - - -

Reference articles

  • Schmid MR et al. (2012): Sleep EEG alterations: effects of different pulse-modulated radio frequency electromagnetic fields.
  • Boutry CM et al. (2008): Dosimetric evaluation and comparison of different RF exposure apparatuses used in human volunteer studies.
  • Huber R et al. (2003): Radio frequency electromagnetic field exposure in humans: Estimation of SAR distribution in the brain, effects on sleep and heart rate.
  • Huber R et al. (2002): Electromagnetic fields, such as those from mobile phones, alter regional cerebral blood flow and sleep and waking EEG.

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

Radiofrequency exposure increased EEG power in the spindle frequency range. Furthermore, delta wave and theta wave activity (Non-REM sleep), and alpha wave and delta wave activity (REM sleep) were affected following both exposure conditions. No effect on sleep architecture and no clear impact of exposure on cognition was observed.
These findings demonstrated that both pulse modulated radiofrequency and pulsed magnetic fields affected brain physiology, and the presence of significant frequency components above 20 Hz was not fundamental for these effects to occur. Because responses were not identical for all exposures, the study does not support the hypothesis that effects of radiofrequency exposure are based on demodulation of the signal only.

Study character:

Study funded by

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