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.
Modulation type: pulsed
Exposure duration: continuous for 30 minutes (in each of 2 sessions)
|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.|
|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|
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.