Abstract
BackgroundHypersensitivity to electromagnetic fields (EMF) is a controversial condition. While individuals with idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) claim to experience health complaints upon EMF exposure, many experimental studies have found no convincing evidence for a physical relation. The aim of this systematic review was to evaluate methodological limitations in experimental studies on symptom development in IEI-EMF individuals that might have fostered false positive or false negative results. Furthermore, we compared the profiles of these limitations between studies with positive and negative results.MethodsThe Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guided the methodological conduct and reporting. Eligible were blinded experimental studies that exposed individuals with IEI-EMF to different EMF exposure levels and queried the development of symptoms during or after each exposure trial. Strengths and limitations in design, conduct and analysis of individual studies were assessed using a customized rating tool.ResultsTwenty-eight studies met the eligibility criteria and were included in this review. In many studies, both with positive and negative results, we identified methodological limitations that might have either fostered false or masked real effects of exposure. The most common limitations were related to the selection of study participants, the counterbalancing of the exposure sequence and the effectiveness of blinding. Many studies further lacked statistical power estimates. Methodically sound studies indicated that an effect of exposure is unlikely.ConclusionOverall, the evidence points towards no effect of exposure. If physical effects exist, previous findings suggest that they must be very weak or affect only few individuals with IEI-EMF. Given the evidence that the nocebo effect or medical/mental disorders may explain the symptoms in many individuals with IEI-EMF, additional research is required to identify the various factors that may be important for developing IEI-EMF and for provoking the symptoms. We recommend the identification of subgroups and exploring IEI-EMF in the context of other idiopathic environmental intolerances. If further experimental studies are conducted, they should preferably be performed at the individual level. In particular, to increase the likelihood of detecting hypersensitive individuals, if they exist, we encourage researchers to achieve a high credibility of the results by minimizing sources of risk of bias and imprecision.
Highlights
Idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) – more commonly known as electromagnetic hypersensitivity (EHS) – is still a matter of scientific debate and much of the controversy has centred on the question of whether the condition is truly caused by electromagnetic fields (EMF)
Studies suggesting an effect of exposure tested 245 (33%) of the IEI-EMF individuals while studies reporting no effect of exposure tested 502 (67%) of the IEI-EMF individuals
We identified one case where the use of an appropriate method to address a key question influenced the rating of another key question: if a sufficient contrast in symptom development between situations with and without exposure is confirmed for everyday exposure situations, it is less likely that the lack of criteria for the exclusion of individuals whose symptoms may be explained by somatic diseases or mental disorders would result in a high risk of bias, indicated as such in the initial rating
Summary
Idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) – more commonly known as electromagnetic hypersensitivity (EHS) – is still a matter of scientific debate and much of the controversy has centred on the question of whether the condition is truly caused by electromagnetic fields (EMF). In contrast to most people, the afflicted individuals claim to suffer from health complaints when using or being in the vicinity of EMF exposure sources, using terms like hypersensitivity or intolerance to EMF to describe their condition [1–4]. While individuals with idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) claim to experience health complaints upon EMF exposure, many experimental studies have found no convincing evidence for a physical relation. The aim of this systematic review was to evaluate methodological limitations in experimental studies on symptom development in IEI-EMF individuals that might have fostered false positive or false negative results. We compared the profiles of these limitations between studies with positive and negative results
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