Topic

Investigation of sleep quality in persons living near a mobile base station - Experimental study on the evaluation of possible psychological and physiological effects under residential conditions

Start

15.06.2005

End

31.03.2008

Project Management

Charité - Universitätsmedizin Berlin

Objective

Indications exist that the sleep parameters, the brain waves (EEG) and the processing of intellectual information are influenced by exposures to mobile phone fields, i.e. at field intensities below accepted limit values. Whether this also applies to the weak fields emitted from base stations has not been studied yet. Epidemiological studies of the influence of high frequency electromagnetic fields on the quality of sleep and well-being have shown contradictory results.

The main focus of this project is to study diverse sleep parameters in population groups living near mobile telecommunication base stations (500 m). The quality of sleep at home will be studied using two methods, survey and registration of physiological parameters (sleep EEG). This will be done in a double-blind study in cross-over design. The evaluation of subjective and objective data should provide information about the influence of high frequency electromagnetic fields on the quality of sleep. The possible influence of psychological components will be taken into account and evaluated. Results of a feasibility study are available.

The objective is to examine the influence of high frequency electromagnetic fields of mobile telecommunication base stations on residents' quality of sleep in a double-blind study.

Results

A three months pilot study has been performed prior to the main study and successfully finished in September 2005. During this period the necessary co-operation between the network operators and the researchers has been established. The network operators agreed to provide the mobile transmitter necessary for the generation of the exposure. An endorsement of the Ethic Commission has been obtained. Furthermore the researchers presented a review of literature about possible influences of electromagnetic fields from base stations on sleep and general well being. The review is included in the final report.

The main study was accomplished at ten locations in five German federal states. All locations were characterised by the absence of mobile phone signals as well as low radiofrequency electromagnetic fields from other sources. The mobile transmitter used for night-time exposure emitted un-modulated and pulse modulated signals according to the GSM-900 and GSM-1800 Standards. The exposure was implemented only during the exposure nights. During day-time as well as during sham exposure nights no signal was emitted. The exposure took place blinded and randomized; the used test signal could not be recognized by mobile phones.

The volunteers were examined in two blocks of six nights each; in all test nights the sleep-EEG was recorded using portable recording devices. The first night served the habituation to the equipment; the data from the following altogether ten nights were evaluated. The five exposure- and five sham-exposure nights were randomized. The total bed time, total sleep time, and sleep onset latency were registered and the sleep efficiency calculated. Morning and evening protocols providing information on subjectively perceived sleep quality (duration, recovery) and the tiredness during the day were filled in every day. At the beginning of the study the sleeping habits of the volunteers as well as psychological parameters and the attitude to mobile communications and other environmental influences were queried once.

Altogether 397 volunteers took part in the study. The sex and age distribution corresponded in about to that of the general population. The frequency of sleep disturbances, psychological problems (e. g. depression) and the attitude to mobile communication (information, concern) corresponded to the general population as well. After inspection and quality check of the raw data for 365 volunteers data on subjective sleep quality and for 335 ones data on objective sleep quality were available for evaluation.

Subjective sleep quality: By means of questionnaires the tiredness at the evening, a potential daytime sleep before a test night, extraordinary burden and events, consumption of coffee, tobacco, alcohol and medications, subjective causes of bad sleep, subjective time in bed, sleep duration, waking time, sleep onset latency, quality of relaxation, sleep efficiency (% sleep time at time in bed) were ascertained. Statistical evaluation of the whole collective has shown that significantly more people stated to have slept bad under sham exposure than under exposure, whereby various private and job-related reasons as well as disturbances were indicated as reasons. During the days before sham exposure significantly more unusual events (wedding, funeral, birth, celebration etc.) happened than during the days before exposure. At the individual level altogether 57 persons showed a significant change in at least one subjective sleep parameter, whereby the tendency was towards a better sleep quality under exposure. A detailed questioning revealed in most cases clear reasons for the worse sleep under sham exposure, like noise, heat, disturbances, problems etc.

Objective sleep quality: The bed time, sleep time, waking time, sleep onset latency of the sleep stage 1 and 2 and sleep efficiency were picked up from the EEG recordings. Statistical evaluation of the entire collective resulted in no significant influence of the exposure on any of these objectively measured sleep parameters. An evaluation on individual basis showed in altogether 36 persons a total of 66 significant changes in individual parameters. Eleven of these persons showed also significant results concerning the subjective parameters; all the others noticed subjectively no difference. On the other hand in 46 volunteers the subjective impression was not reflected by the sleep EEG. For the objective sleep parameters the sleep quality was poor under exposure, whereby according to the questionnaires predominantly reasons other than electromagnetic fields could be identified for bad sleep. The proportion of persons showing significant changes in a certain sleep parameter remained for all subjective and objective parameters below the 5 %, which were expected purely by chance. A systematic association between the measured field strength and the observed changes of sleep quality could not be established.

The influence of psychological factors has been investigated exclusively during sham exposure night to exclude a possible physiological influence of electromagnetic fields. The sleep onset latency increased with increasing distance from the transmitter, which is probably a coincidence. Concerns related to the base stations, but not to mobile communication in general, resulted in significantly prolonged subjective sleep onset latency and in longer objective and subjective waking time during the night as well as a diminished subjective and objective sleep quality. This has to be assessed as a clearly worsened sleep quality due to a nocebo effect. The recovery during the sleep remained unchanged. Dealing with the topic “mobile communication” was correlated with prolonged time in bed and total sleep time.

The final report (3323 KB) with an Appendix (50 KB) can be downloaded as a PDF-file in German with English abstract:

Final report

Appendix

References

• Danker-Hopfe H, Dorn H, Bornkessel Ch, Sauter C (2010): Do mobile phone base stations affect sleep of residents? Results from an experimental double-blind sham-controlled field study. Am. J. Hum. Biol. DOI 10.1002/ajhb.21053

Conclusions

The presented results do not support the existence of a physiological influence of electromagnetic fields from base stations on subjective and objective sleep quality. Clear effects on the sleep quality solely due to the presence of a base station combined with concern about possible health risks could be verified. The results show, that not the exposure does negatively influence the sleep quality, but the worries concerning possible health consequences; this is the case even if the transmitter is not operating.