Methodological limitations in experimental studies on symptoms in individuals with idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) - review

Abstract

Methodological limitations in experimental studies on symptoms in individuals with idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) - review Schmiedchen K, Driessen S, Oftedal G. Methodological limitations in experimental studies on symptom development in individuals with idiopathic environmental intolerance attributed to electromagnetic fields (IEI- EMF) - a systematic review. Environ Health. 2019 Oct 22;18(1):88. doi: 10.1186/s12940-019-0519-x. Abstract BACKGROUND: Hypersensitivity 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. METHODS: The 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. RESULTS: Twenty-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. CONCLUSION: Overall, 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. EXCERPT: At present, it is not clear whether further provocation or intervention studies would provide new insight, but if further experimental studies are conducted, they should preferably be performed at the individual level. In order to increase the likelihood of detecting hypersensitive individuals, if they exist, we encourage researchers to achieve a high credibility of the results by minimizing of sources of risk of bias and imprecision. In any such study, efforts must be made to identify and include any individuals whose symptoms are caused by physical effects of the EMF exposure. Open access paper: ehjournal.biomedcentral.com MY NOTE: Some scientists have argued that the provocation studies which this review paper evaluated employ an inappropriate methodology to test individuals with electromagnetic hypersensitivity (EHS, or IEI-EMF). Provocation studies assume that symptoms appear immediately after an exposure to EMF ignoring the fact that in many instances there is a time lag between an EMF exposure and experience of symptoms. Thus, I concur with the authors' suggestion that further provocation studies are likely a waste of time. I would argue we need new paradigms to study EHS.

AI evidence extraction

Main findings

This systematic review included 28 blinded experimental studies exposing IEI-EMF individuals to different EMF exposure levels and assessing symptoms during or after exposure. The authors report that many studies (both with positive and negative results) had methodological limitations that could produce false positives or mask real effects; however, methodically sound studies indicated an effect of exposure is unlikely, and overall the evidence points towards no effect of exposure.

Outcomes measured

• Symptom development during or after blinded EMF exposure trials
• Methodological limitations/risk of bias in provocation studies (participant selection, exposure sequence counterbalancing, blinding effectiveness, statistical power estimation)

Limitations

• Review focuses on methodological limitations of included studies; specific EMF parameters (frequency, SAR, sources) are not described in the provided abstract.
• Many included studies reportedly had limitations in participant selection, counterbalancing of exposure sequence, and blinding effectiveness.
• Many studies lacked statistical power estimates (as reported by the review).

{
    "study_type": "systematic_review",
    "exposure": {
        "band": "unknown",
        "source": "unknown",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Individuals with idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF)",
    "sample_size": 28,
    "outcomes": [
        "Symptom development during or after blinded EMF exposure trials",
        "Methodological limitations/risk of bias in provocation studies (participant selection, exposure sequence counterbalancing, blinding effectiveness, statistical power estimation)"
    ],
    "main_findings": "This systematic review included 28 blinded experimental studies exposing IEI-EMF individuals to different EMF exposure levels and assessing symptoms during or after exposure. The authors report that many studies (both with positive and negative results) had methodological limitations that could produce false positives or mask real effects; however, methodically sound studies indicated an effect of exposure is unlikely, and overall the evidence points towards no effect of exposure.",
    "effect_direction": "no_effect",
    "limitations": [
        "Review focuses on methodological limitations of included studies; specific EMF parameters (frequency, SAR, sources) are not described in the provided abstract.",
        "Many included studies reportedly had limitations in participant selection, counterbalancing of exposure sequence, and blinding effectiveness.",
        "Many studies lacked statistical power estimates (as reported by the review)."
    ],
    "evidence_strength": "moderate",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "IEI-EMF",
        "electromagnetic hypersensitivity",
        "EHS",
        "provocation studies",
        "blinded experimental studies",
        "PRISMA",
        "methodological limitations",
        "nocebo effect",
        "risk of bias"
    ],
    "suggested_hubs": []
}

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