Systematic literature study on possible effects of exposure to radiofrequency electromagnetic fields on human cognitive performance

Background

The World Health Organization (WHO) has been studying the potential health effects of exposure to electromagnetic fields (EMFs) for decades. The Environmental Health Criteria (EHC) monographs are the WHO’s risk assessments for chemical, biological and physical health factors. These monographs are drawn up by independent scientists and are the result of a thorough and critical review of the entire body of research on a specific chemical or physical factor such as electromagnetic fields¹. To date, the WHO has published three EHC monographs on these fields, including static², extremely low-frequency (ELF)³ and radiofrequency (RF) fields. The last EHC monograph on radiofrequency electromagnetic fields was published in 1993⁴. In view of the large number of new publications in this field, this monograph is currently being comprehensively updated, which will lead to a new EHC monograph on the subject.

To ensure that the EHC monograph is based on the most up-to-date knowledge and includes all available scientific evidence on particularly relevant diseases or symptoms (endpoints), the WHO has commissioned a series of systematic reviews to address specific questions (see Spotlight on EMF Research from 24 April 2024⁵). One such question is whether the available epidemiological studies on humans can be used to deduce possible effects of exposure to these radiofrequency fields on human cognitive performance.

Radiofrequency electromagnetic fields are used to transmit information in radio applications. The investigation of the possible effects of these fields on cognitive performance is mainly due to the comparatively high exposure of the brain that can occur during mobile phone calls. Given the widespread use of wireless technology among workers and the general population, even small changes in cognitive performance metrics such as accuracy, reaction time or speed can have a significant impact.

Objective

The WHO commissioned specialised scientists from the BfS and other institutions to carry out a systematic evaluation of the scientific literature on the possible effects of short-term exposure to radiofrequency electromagnetic fields on human cognitive performance. To this end, all available peer-reviewed scientific literature relevant to this issue was to be systematically identified, evaluated and analysed.

Methods and implementation

A protocol was drawn up in advance and published in a peer-reviewed scientific journal. This protocol transparently set out the methodology and evaluation criteria for conducting the study⁶. The research question was formulated according to the “PECO” scheme, which defines the population (P), exposure (E), comparator (C) and outcome (O) to be investigated as follows: In humans (P), what are the direct effects of exposure to radiofrequency electromagnetic fields in the frequency range from 100 kilohertz (kHz) to 300 gigahertz (GHz) (E) on cognitive performance (O) compared to no or lower exposure (C)?

The study included randomised experimental studies with parallel-group and cross-over design in which at least two exposure levels (including a sham-exposed or control group) were tested under controlled laboratory conditions. Participants were not allowed to be informed about their exposure status. Studies were excluded if they exhibited insufficient exposure contrast, a lack of exposure characterisation, or co-exposure to electromagnetic fields outside the specified frequency range, or if they were clearly not randomised. In the period between May 2021 and March 2023, electronic searches were carried out in the databases PubMed (NLM), Embase, Scopus, Web of Science and the EMF-Portal, with no restrictions on publication date or language. The studies identified in this way underwent a multi-stage evaluation procedure to check whether they met the defined inclusion criteria. This procedure was used to compile the final set of included studies, from which the relevant data for the systematic review was then extracted.

The quality of these studies was evaluated using a procedure established for clinical studies, and it determines the severity of various risks of falsification and bias. For various measures and characteristics of cognitive performance, the available data was summarised and meta-analyses were carried out where the database permitted. An evaluation was made of whether and to what extent the data could be used to derive an effect on the various areas of cognitive performance. Confidence in these results was then evaluated using the concept known as Grading of Recommendations Assessment, Development and Evaluation (GRADE), as recommended by the non-profit organisation Cochrane. The results were published in the special issue "WHO assessment of health effects of exposure to radiofrequency electromagnetic fields: systematic reviews" of the journal Environment International, which specialises in systematic reviews⁷.

Results

After the removal of duplicates, the database search yielded 23,450 studies. Once the inclusion criteria were checked, 76 studies were identified that contained the level of knowledge relevant to the research question. Accuracy and speed in the cognitive areas of orientation and attention, memory, perception, motor performance, and concept formation and reasoning were extracted and analysed from the studies as measures of cognitive performance.

No reliable evidence was found that people’s cognitive performance is impaired in any of the investigated cognitive areas in the event of acute exposure to radiofrequency electromagnetic fields. Confidence in the evidence is moderate or even high for most areas or their subcategories due to the majority of relatively high-quality studies, comparatively consistent results and large numbers of participants.

It is therefore quite clear from the available data that no influence on cognitive performance is to be expected below the existing limit values. The studies for which there is a high risk of bias were in most cases not double-blinded, and the exposure generation and characterisation did not allow precise determination of exposure.

Literatur

1) World Health Organization. Radiation and health - Health risk assessment 2024

2) World Health Organization. Static fields: World Health Organization; 2006

3) World Health Organization. Extremely low frequency fields: World Health Organization; 2007.

4) World Health Organization. Electromagnetic fields (300 Hz to 300 GHz): World Health Organization; 1993.

5) Spotlight on "WHO assessment of health effects of exposure to radiofrequency electromagnetic fields: systematic reviews", a special series in Environment International.

6) Pophof, Blanka, et al. "The effect of exposure to radiofrequency electromagnetic fields on cognitive performance in human experimental studies: A protocol for a systematic review." Environment international 157 (2021): 106783.

7) Pophof, Blanka, et al. "The effect of exposure to radiofrequency electromagnetic fields on cognitive performance in human experimental studies: Systematic review and meta-analyses." Environment International (2024): 108899.