この研究は、若い男性被験者（n=20）に就寝前に30分間、パルス化900MHzのRF EMF（2Hzパルス変調、10g平均SARの空間ピーク値2 W/kg）のばく露を与え、その後、終夜の脳電図（EEG）測定を行った。各被験者は同じ実験を2週間の間隔で2回行った。終夜のノンレム睡眠時のEEGのパワースペクトルのトポグラフィー分析を行った。その結果、ばく露に関連したデルタ・シータ波帯での増加が前頭-中心部で見られたが、紡錘波帯では変化がなかった､と報告した。前回の研究では、個人差が大きいものの、個人によってはデルタ・シータ波帯および紡錘波帯の活動性に影響が見られたので、この影響の個人内変動を見るのが今回の目的であった。しかし今回は影響そのものが確認されなかった､と述べている。
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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.
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
ばく露時間: continuous for 30 minutes (in each of 2 sessions)
|ばく露時間||continuous for 30 minutes (in each of 2 sessions)|
|Repetition frequency||2 Hz|
peak-to-average ratio of 4; higher harmonics were reduced by applying a 20 Hz Gaussian low-pass filter to a rectangular pulse sequence
|Distance between exposed object and exposure source||110 mm|
|ばく露装置の詳細||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||推定値||10 g||peak value for whole head|
|SAR||2.12 W/kg||spatial average||推定値||1 g||peak value for lateral cortex, ± 12% standard deviation|
|SAR||0.62 W/kg||-||推定値||-||for thalamus, ± 35% standard deviation|
|電力||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.