Study type: Medical/biological study (experimental study)

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

Published in: J Sleep Res 2012; 21 (1): 50-58

Aim of study (acc. to author)

To study which electromagnetic field parameters may be responsible for previously reported results (see "related articles") on electrical brain activity during sleep. The authors hypothesized that pulse modulation components in the sleep spindle frequency range (e.g. 14 Hz) could act as potential mediators (the majority of previous studies found an influence of radiofrequency exposure in this frequency range). Additionally, pulse modulation at 217 Hz (component of the GSM signal) was studied.

Background/further details

Cognitive tasks were also included during exposure with the aim to elucidate previous inconclusive results regarding the effects of exposure to pulse modulated radiofrequency electromagnetic fields on cognition.
30 men participated. The protocol consisted of six study nights (three exposure nights at weekly intervals, each preceded by an adaptation night). Exposure lasted 30 min and ended 10 min before subjects had to go to bed.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 900 MHz
Modulation type: pulsed
Exposure duration: continuous for 30 min.
  • SAR: 2 W/kg peak value (10 g)
Exposure 2: 900 MHz
Modulation type: pulsed
Exposure duration: continuous for 30 min.
  • SAR: 2 W/kg peak value (10 g)

Exposure 1

Main characteristics
Frequency 900 MHz
Type
Exposure duration continuous for 30 min.
Additional info pulse modulated at 14 Hz
Modulation
Modulation type pulsed
Pulse width 2.3 ms
Repetition frequency 14 Hz
Pulse type rectangular
Additional info

crest factor = 30.95

Exposure setup
Exposure source
Distance between exposed object and exposure source 115 mm
Setup subjects sat on a chair with their heads positioned between the antennas at a distance of 115 mm from the head with their centres 42 mm vertically above the ear canal; the left hemisphere of the brain was exposed
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 2 W/kg peak value - 10 g -

Exposure 2

Main characteristics
Frequency 900 MHz
Type
Exposure duration continuous for 30 min.
Additional info pulse modulated at 217 Hz
Modulation
Modulation type pulsed
Pulse width 0.577 ms
Repetition frequency 217 Hz
Pulse type rectangular
Additional info

crest factor = 8

Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
SAR 2 W/kg peak value - 10 g -

Reference articles

  • Boutry CM et al. (2008): Dosimetric evaluation and comparison of different RF exposure apparatuses used in human volunteer studies.
  • Huber R et al. (2005): Exposure to pulse-modulated radio frequency electromagnetic fields affects regional cerebral blood flow.
  • 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. (2000): Exposure to pulsed high-frequency electromagnetic field during waking affects human sleep 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)

The data showed that pulse modulated radiofrequency electromagnetic fields altered the brain physiology. Specifically, 14 Hz pulse modulated exposure led to an increase in the EEG power spectrum during Non-REM sleep in the spindle frequency range (in the second Non-REM sleep episode, i.e. approx. 2-3 h after sleep onset). This suggests that the 14 Hz pulse modulation component, which is in the proximity to the physiological sleep spindle frequency, is one potential mediator of the observed effects on the sleep EEG. (A sleep spindle is a burst of oscillatory brain activity visible on an EEG that occurs during sleep stage 2. It consists of 12-14 Hz waves that occur for at least 0.5 seconds).
A similar but non-significant increase was also observed following the 217 Hz pulse modulated condition.
The exposure-induced effect showed a considerable individual variability (the majority of participants showed an increase, while some showed no change or even a decrease following the 14 Hz pulse modulated exposure).
There were no effects on sleep architecture, i.e. the responses seen in the EEG did not result in any changes of the sleep quality.
Some small effects on EEG spectral power during REM sleep were found, but there was no clear pattern.
Regarding cognitive performance, no clear exposure-related effects were found. Reaction speed tended to be slower with 217 Hz pulse modulation in all tasks, whereas accuracy of performance was largely unaffected.
In conclusion, the data provide further evidence for short-term effects of radiofrequency electromagnetic fields exposure on the sleep EEG in healthy, young male adults. In particular, pulse modulation frequency components within a physiological range were sufficient to induce these effects.

Study character:

Study funded by

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