Medical/biological study (experimental study)

Inter-individual and intra-individual variation of the effects of pulsed RF EMF exposure on the human sleep EEG med./bio.

By: Lustenberger C, Murbach M, Tushaus L, Wehrle F, Kuster N, Achermann P, Huber R

Published in: Bioelectromagnetics 2015; 36 (3): 169-177

Aim of study (acc. to author)

The effects of exposure of young meninges to a 900 MHz electromagnetic field prior to sleep on the brain activity during sleep should be investigated.

Background/further details

The study aimed to investigate inter-individual variation and intra-individual stability of the effects of pulsed radiofrequency exposure on human sleep EEG, as former studies revealed striking inter-individual differences and intra-individual stability (i.e. reproducibility of effects in the same subject) has not been well studied so far.
A total of 20 healthy male subjects participated in 4 night-sessions with a 1-week interval (one night per week on the same weekday). In 2 of those nights, subjects were exposed to the electromagnetic field prior to their scheduled bedtime, in the 2 other nights, subjects were sham-exposed. In a randomized, double-blind, cross-over study design, subjects had one of the 2 exposure orders: sham-exposure/exposure/sham-exposure/exposure or exposure/sham-exposure/exposure/sham-exposure. After real or sham exposure, an EEG cap was applied to the subjects resulting in a 30 min time window between end of exposure and start of sleep recording (lights out).
One subject was excluded from analysis due to poor sleep and EEG signal quality , so a total of 19 subjects were evaluated.

Endpoint

effects on the neurological system: sleep EEG

Exposure

- 900 MHz
- mobile communications
- mobile phone

Exposure	Parameters
Exposure 1: 900 MHz Modulation type: pulsed Exposure duration: continuous for 30 minutes (in each of 2 sessions)	SAR: 2 W/kg spatial average (10 g) (peak value for whole head) SAR: 2.12 W/kg spatial average (1 g) (peak value for lateral cortex, ± 12% standard deviation) SAR: 0.62 W/kg (for thalamus, ± 35% standard deviation) power: 4 W (forward power to the antenna, ± 6% standard deviation)

Exposure 1

Main characteristics

Frequency	900 MHz
Type	electromagnetic field
Exposure duration	continuous for 30 minutes (in each of 2 sessions)

Modulation

Modulation type	pulsed
Repetition frequency	2 Hz
Additional info	peak-to-average ratio of 4; higher harmonics were reduced by applying a 20 Hz Gaussian low-pass filter to a rectangular pulse sequence

Exposure setup

Exposure source	patch antenna
Distance between exposed object and exposure source	110 mm
Setup	a lateral patch antenna in a plastic box-casing was used to expose left head hemisphere; an identical box-casing was installed on the right side to prevent knowledge about the exposure; exposure system was fully computer controlled
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
SAR	2 W/kg	spatial average	estimated	10 g	peak value for whole head
SAR	2.12 W/kg	spatial average	estimated	1 g	peak value for lateral cortex, ± 12% standard deviation
SAR	0.62 W/kg	-	estimated	-	for thalamus, ± 35% standard deviation
power	4 W	-	-	-	forward power to the antenna, ± 6% standard deviation

Measurement and calculation details

SAR efficiency was numerically estimated with anatomical human head models from the Virtual Population, using the simulation platform SEMCAD X; validation measurements were performed with dosimetric SAR probes in the specific anthropomorphic mannequin (SAM) with a near-field scanner; the uncertainty for the peak spatial average SAR 10g assessment stayed below 8% standard deviation corresponding to the obtained 10.4% deviation between simulation and measurement of the SAM head; variability of the peak spatial average SAR 10g remained below 15% standard deviation

Reference articles

Murbach M et al. (2014): Modeling of EEG electrode artifacts and thermal ripples in human radiofrequency exposure studies
Schmid MR et al. (2012): Sleep EEG alterations: effects of pulsed magnetic fields versus pulse-modulated radio frequency electromagnetic fields
Murbach M et al. (2012): Exposure system to study hypotheses of ELF and RF electromagnetic field interactions of mobile phones with the central nervous system
Christ A et al. (2010): Age-dependent tissue-specific exposure of cell phone users

Exposed system:

human
partial body: left side of the head

Methods Endpoint/measurement parameters/methodology

sleep: sleep quality and mood in the morning (questionnaire), sleep latency, REM sleep latency, REM sleep duration, wake after sleep onset (visual scoring in EEG), spectral power, sleep spindle and delta wave-theta wave activity during non-REM sleep (polysomnography including EEG, EOG and EMG during 8 h nighttime sleep period)

Investigated system:

investigation on living organism

Investigated organ system:

brain/CNS

Time of investigation:

after exposure

Main outcome of study (acc. to author)

The delta wave-theta wave activity during non-REM sleep was significantly increased in several fronto-central brain regions after exposure compared to sham exposure sessions. However, this effect was not reproducible in the same subjects. All other parameters did not show significant differences between exposure and sham exposure conditions at all and no inter-individual or intra-individual correlations.
The authors conclude that no reproducible effects of exposure of young males to a 900 MHz electromagnetic field prior to sleep on the brain activity during sleep were observed.

Study character:

medical/biological study
experimental study
full/main study
double-blind study, cross-over study

Study funded by

Forschungsstiftung Mobilkommunikation (FSM; Research Foundation on Mobile Communication; at the Swiss Federal Institute of Technology Zurich (ETH)), Switzerland
Swiss National Science Foundation (SNF)

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