To study the potential impact of radiofrequency electromagnetic fields of transmitters on the sleep quality of nearby residents, a new study design is presented: In a double-blind study the effect of on-site shielding (i.e. in the bedrooms of the subjects), rather than of additional exposure, was examined (cf. publication 11333).
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Data of 44 subjects were analysed (data were partly pooled with data of another study, the so-called EPROS study). The subjects suffered from permanent and severe sleep disturbances and were deeply convinced that environmental radiofrequency electromagnetic fields caused their problems.
Sham-shielding was performed by using a sham shield.
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80 MHz–2.5 GHz
Exposure duration: continuous
|Frequency||80 MHz–2.5 GHz|
|Chamber||A mobile shield was used to examine the response of the subjects to the absence or reduction of the electromagnetic exposure. The cubic shield was made of double-layered conductive tissue and enclosed the bed completely (also on the floor). The shield was erected and taken down every day.|
|Setup||After an adaptation night, polysomnographic measurements were recorded from each volunteer during at least 3 nights under each of the following conditions: real shield, sham shield, and unshielded control, in random order. The measurement data were kept double-blinded.|
|Sham exposure||A sham exposure was conducted.|
|Additional info||The median attenuation by the shield of the total immission was 19.3 dB (interquartile between 15 and 24 dB). A second, virtually undistinguishable, sham shield was transparent to EMF.|
No parameters are specified for this exposure.
Most of the subjects exhibited an increased electrosensitivity. The measurements of the radiofrequency electromagnetic fields (EMF) did not confirm volunteer's expectations to have atypically increased EMF levels within their bedrooms. The data showed a non-significant trend to improved sleep quality with the EMF levels in general. In particular, no statistical significant dependency could be found with mobile phone field levels.
For a predominant number the subjective conviction of volunteers that radiofrequency electromagnetic pollution was the cause of their sleep disturbance could be falsified. The pooled analysis resulted in statistically significant placebo-effects for subjective sleep parameters. This was confirmed by volunteer-based analysis. For 18% of volunteers it could be demonstrated that their belief in shielding improved sleep (placebo-effect).
The investigations did not indicate adverse health effects on sleep from radiofrequency electromagnetic fields in general and from mobile phone fields in particular. However, the study showed that subtle effects of electromagnetic fields on the sleep onset behaviour (increased sleep onset latency times with decreasing exposure) might be possible. This finding is of particular importance regarding potential interaction mechanisms of weak (non-thermal) radiofrequency electromagnetic fields and should be verified by further investigations.