Research at the Competence Center for Sleep Medicine

The steadily increasing use of digital mobile communication systems has raised public concern about possible health effects from electromagnetic fields (EMF). In Germany, such concerns were reviewed in annual surveys conducted from 2003 to 2006 within the German Mobile Telecommunication Research Programme (DMF). Sleep disturbances were among the most prevalent complaints. Approximately 1% of the respondents indicated to suffer from sleep disturbances which they claimed to be due to digital mobile communication systems. 

However, whenever a possible causality between EMF emitted by mobile phones and sleep disturbances is considered, it should be taken into account that sleep disturbances are very common in the general population with a prevalence rate of 10-20%.

Conclusive results are expected from studies in which the exposure, e.g. from mobile phones, mobile phone base stations, occupationally used TETRA-handsets WIFI devices, is experimentally varied. In such a study design each participant is exposed to both a sham (sham exposure) and an active signal and the two conditions are compared within each participant (cross-over design). Neither the participants nor the investigators are aware of the actual exposure condition, i.e. the experimental procedure is double-blind. Double-blinding is crucial, since it reduces or eliminates the probability that the results will be affected by conscious or unconscious bias. In our studies sleep quality is not only assessed subjectively but also measured at an objective level. This has been done by our lab in several research projects investigating different study samples (healthy youong males between 20 and 30 years, as well as elderly women and men aged between 60 and 80 years) under various radio frequency exposure signals.

These research projects have been/are funded by the Federal Office for Radiation Protection (BfS), the Federal Agency for Digital Radio of Security Authorities and Organisations (BDBOS) and the Swiss Research Foundation for Electricity and Mobile Communication (FSM).

For two of the research projects final reports (in German with an English summary) are available on the website of the Federal Office for Radiation Protection.

In a further experimental field study that took place in the home environment of the participants it was investigated whether sleep is affected by EMF emitted by mobile phone base stations. 397 subjects were recruited for this double-blind, sham-controlled cross-over study. The study was performed in 10 villages in various parts of Germany. Participants were excluded if they lived in a distance of more than 500 meters from the mobile phone base station. Outcome measures were subjective and objective sleep quality assessed after real or sham exposure.A feasability study has been successfully completed in the run-up to the field study.

The following publications can be assigned to this research area: Danker-Hopfe et al. (216, 2011, 2010), Eggert et al. (2015), Sauter et al. (2015, 2011), Dorn et al. (2014).

In our ongoing study acute effects of GSM- and TETRA-related signals on the central nervous system in a sample of 60 to 80 years old healthy men are investigated. A forthcoming study starting presumably in December 2017 aims at studying possible WIFI effects on sleep and on the consolidation of declarative, procedural end emotional memories during sleep. Potential participants, i.e. young healthy men aged between 18 and 30 years may find here the study information.

There are several physiological [Multiple Sleep Latency Test (MSLT), Multiple Wakefulness Test (MWT), Pupillographic Sleepiness Test (PST)] and psychological tools to assess different aspects of attention (tonic and phasic alertness, divided attention, selective attention, vigilance). A focus of our working group is to investigate possible interrelationships between these indicators of attention. In an ongoing project, it is examined whether pupillographic variables are associated with results of the MSLT in different groups of patients. Moreover, reference data for some of the above mentioned assessment tools as well as for the Epworth Sleepiness Scale have been developed in our laboratory (Sauter et al., 2007; Eggert et al., 2012; Sauter et al., 2013). Recently, normative values for the PST and for a vigilance task based on the Mackworth clock test have been extended for the age range from 60 to 79 years. Many studies in our lab addressed also the implementation of MSLT and MWT in DGSM-accredited sleep laboratories ((Danker-Hopfe et al., 2006; Sauter und Danker-Hopfe, 2010).

Sleep and memory are subject to age-dependent variations. Middle- and old-aged subjects among others show a reduced total sleep time, sleep efficiency, slow wave sleep, REM sleep and number of sleep spindles when compared to young subjects. The number of nocturnal arousals and total time spent awake after sleep onset are, on the other hand, increased in the elderly. Both declarative and procedural memory are also affected by the aging process.

Considering the striking indications of the importance of sleep for memory consolidation in young subjects, studies, in which the relevance of sleep for memory consolidation in elderly subjects is investigated, are of particular interest. This issue has been addressed in a large research project (160 healthy old participants ranged between 60 to 85 years) initially funded by the Deutsche Forschungsgemeinschaft.

Studies in young healthy volunteers provided evidence of a beneficial impact of an anodal time-varied transcranial direct current stimulation (tDCS) during early - slow wave rich - sleep on declarative memory but not on procedural memory (Marshall et al., 2006). In a recent study it was investigated whether sleep-dependent memory consolidation can also be affected by slow oscillating tDCS in a population of elderly subjects. In contrast to a younger subject group, sotDCS did not show effects on memory consolidation in the elderly (Eggert et al., 2013).

An ongoing study in young and elderly subjects aims at investigating whether there are gender- and age-specific differences in the sleep-dependent memory consolidation.

Attention deficit hyperactivity disorder (ADHD) is characterized by a sustained pattern of impulsive behavior, disorganization, impaired attention, emotional instability and hyperactivity (Naseem et al. 2001). For children with ADHD a higher daily activity compared to healthy controls is well-known (Dane et al. 2000), as well as various sleep disorders, including those caused by frequent limb movements (Datta and Vella, 2009). This increased motor activity during sleep was also observed in adults with ADHD (Sobanski et al. 2008). In addition, there is evidence of an increased daily activity in adult ADHD-patients (Boonstra et al. 2007). In a study conducted in our laboratory the motor activity of adult ADHD-patients compared to healthy sex- and age-matched controls is investigated with actigraphy and the suggested immobilization test. Actigraphy is a method based on a wristwatch-like device that detects motor activity of the body. Consequently, activity values for day and night can be determined. The suggested immobilization test is primarily used in clinical trials related to the restless legs syndrome, to investigate the urge to move legs in the evening and to assess the effect of immobilization on sensory and motor symptoms, respectively (Haba-Rubio et al. 2006).

The Bundeswehr currently conducts a pilot study to introduce occupational health managements. One of the pillars of this occupational health management is stress prevention, which includes a module sleep coaching. This module was developed and implemented by our lab; it is performed by the psychologists of the Bundeswehr, who have been trained by us.

Furthermore the Ministry of Defense funded an ongoing scientific study to evaluate the efficacy of an outpatient group training for a restorative sleep. The 4-week training program is delivered by one of our scientific staff members. Prior to and following the program sleep is evaluated at the subjective and objective level.

Our sleep lab initiates and participates in clinical trials of patients with different sleep disorders (RLS, PLMS, primary insomnia and narcolepsy). If you are interested in participating in a clinical trial in our sleep laboratory, please contact Frau Ney or Frau Steinberg on t: +49 30 450 517 577.