Our data suggested that short-term EMF exposure did not exert a significant effect on the BP of the participants in either the IEI-EMF or control group. This finding is in line with that of previous provocation studies, which have reported that short-term EMF exposure does not affect BP [17, 19, 36]. Our data also indicated that short-term EMF exposure does not affect HRV, which is also consistent with the findings of previous studies [37, 38], in which no change in HRV associated with EMF exposure was reported.
We searched Medline, PubMed, and Web of Science for research articles on double blind provocation studies that included participants with IEI-EMF by using the following keywords: “phone,” “base station,” “non-ionizing radiation,” “electromagnetic field,” “hypersensitivity,” “intolerance,” and “provocation.” A total of 12 articles that measured the physiological parameters of participants with IEI-EMF were published till the end of 2019 [17,18,19,20, 25, 26, 39,40,41,42,43,44]. In all the studies, participants could not accurately identify EMF exposure, and short-term exposure to EMF was not related to subjective symptoms or well-being. Specifically, three studies investigating BP [17, 19, 36] in a total of 150 participants with IEI-EMF and 112 controls did not observe an association between radio frequencies (900 MHz NMT, 900 MHz GSM, and 1800 MHz GSM) and SBP or DBP. Similarly, five studies investigating HR [17,18,19, 25, 26] in a total of 303 participants with IEI-EMF and 512 controls did not observe an association between EMF exposure and HR. These results are compatible with the findings of our study.
The 12 previous studies [17,18,19,20, 25, 26, 39,40,41,42,43,44] used exposure durations ranging from 10 min to 3 h, and the exposure intensity was lower than the intensity in the safety guidelines of the ICNIRP, which recommends a power density of 10 W/m2 for the general public  for radio frequencies ranging between 10 and 300 GHz. However, most of the studies were not conducted in EMF-shielding spaces; thus, participants were not shielded from environmental EMF. Therefore, one of the plausible reasons why the studies did not observe physiological changes induced by EMF is the interference caused by environmental EMF. In our study, the experiment was conducted in a laboratory that could block EMF from outside sources, thereby minimizing the interference of environmental EMF. Another plausible reason is that the dosage administered was too small to introduce an effect. Although the power of EMF we administered in the experiments was one-tenth of the ICNIRP maximum recommended environmental exposure value, it is much higher than those administered in the previous studies [17,18,19,20, 25, 26, 39,40,41,42,43,44], and such a high level is unlikely to be encountered under normal living conditions. In Taiwan, the average power density of 5,677 randomly selected spots for measurement by the Environmental Protection Administration between 1999 and 2021 was 0.23 W/m2, and only 18 (0.3%) of the measured values were higher than 1 W/m2 . All the participants with IEI-EMF in our study reported experiencing symptoms in their daily lives, and the intensity of EMF exposure administered in our experiment was sufficient to provoke the symptoms if they are actually induced by EMF.
In our study, although four participants in the IEI-EMF group and one in the control group identified both the sham and provocation sessions correctly, none of them gave correct answers in the second trial. Accordingly, we determined that none of the participants could actually perceive the EMF exposure. This finding is consistent with the results of the previous studies [17,18,19,20, 25, 26, 39,40,41,42,43,44], all of which reported that participants could not accurately detect EMF exposure. This finding is also in line with the WHO’s statement in its Fact Sheet that there is no scientific basis for the association between IEI-EMF symptoms and EMF exposure . We had planned to consider participants who reported the exposure status correctly in three consecutive two-session tests as being able to perceive the EMF exposure and to invite them to participate in further tests to determine the lowest level of EMF they can detect. Because none of the participants were able to even pass two consecutive tests, this part of the experiment protocol could not be executed.
Our study results also indicated that the symptoms reported by the participants were not related to EMF provocation. In fact, substantial overlaps were observed in the most commonly reported symptoms during the provocation and sham sessions between the IEI-EMF and control groups, and the odds ratios (ORs) of these symptoms were similar between the two groups. In the control group, the OR could not be calculated for five symptoms because no one reported these symptoms in the sham session without reporting them in the provocation session (Table 2). Of these symptoms, one participant reported nausea in the provocation session, but not in the sham session, and two such cases of desire to cough were observed. Because we used the Electromagnetic Hypersensitive Questionnaire to determine whether a participant should be placed in the IEI-EMF or control group, the symptoms reported by the participants in the control group were unlikely to be related to EMF exposure. Additionally, neither nausea nor desire to cough were related to EMF exposure in the IEI-EMF group. Furthermore, if there is an association between EMF and a given symptom, the OR in the IEI-EMF group should be larger than that in the control group. However, even when we combined data from the two groups under the assumption that they have the same OR, the p value of the OR associated with nausea was 0.34, and that of the OR associated with desire to cough was 0.63. Therefore, these symptoms could not be determined as associated with EMF exposure. These findings further support the inference that the symptoms reported by the participants were not related to EMF provocation. Some studies have proposed the use of models to illustrate how patients attribute idiopathic symptoms to various environmental factors. According to these models, in an attempt to identify the cause of their symptoms, patients are inclined to attribute these symptoms to environmental factors they have recently been exposed to. Their belief that these factors are causing their symptoms in turn leads them to develop further symptoms of intolerance towards the factors .
Previous provocation studies [25, 26] have found nocebo-like effects of EMF exposure on the physiological parameters of participants. To the best of our knowledge, however, this study is the first to explore the changes in the participants’ physiological parameters when they perceived exposure to EMF, irrespective of whether they have actually been exposed to EMF. The results revealed that except for the LF/HF ratio in the IEI-EMF group, the differences in physiological parameters were generally larger between the sessions with and without perceived EMF exposure than between the sessions with and without actual EMF exposure (Table 3). This indicates that the effects of perception on changes in physiological parameters are larger than those of actual EMF exposure. In addition, we found that the controls had elevated HR when they perceived EMF exposure, but this was not found in the participants with IEI-EMF. In fact, the participants with IEI-EMF had decreased (instead of elevated) HR when they perceived the exposure compared with when they did not, although the difference did not reach statistical significance. We speculate that the controls did not expect that they could perceive the existence of EMF and were thus surprised when they thought they did, which may have led to increases in HR. Further studies exploring the mechanism underlying this phenomenon might help elucidate the etiology of IEI-EMF.
This study has some limitations. First, according to the Working Group Meeting Report of the WHO Workshop on Electrical Hypersensitivity, IEI-EMF is defined as “symptoms that are experienced in proximity to, or during the use of, electrical equipment, and that result in varying degrees of discomfort or ill health in the individual and that an individual attributes to activation of electrical equipment” . Therefore, IEI-EMF is defined on the basis of subjective symptoms and has no objective criteria for verification. However, this is a limitation of all IEI-EMF studies in general, not just of our study . Second, it is possible that a certain level of EMF higher than that administered in this study may introduce remarkable physiological changes or symptoms in humans, but the purpose of this study was to assess physiological changes and symptoms associated with exposure to EMF in real life, not to test the limit of human beings. Moreover, exposing participants to such high doses of EMF might be considered unethical. Third, we did not include new technologies such as 4G and 5G because they were not widely used when this study was initiated, and further studies should be conducted to evaluate their potential effects. Fourth, we did not match age and sex in the selection of controls, and age and sex differences existed between the two groups. Although these factors might affect physiological parameters, the effects are generally unremarkable. For example, the diagnostic criteria for hypertension are generally the same, irrespective of age or sex. Nevertheless, additional studies with age and sex matching may address this issue directly. Fifth, we used OR to evaluate the associations between symptoms and EMF exposure. When no participant had a sham-positive/provocation-negative status, the OR could not be calculated; thus, the potential effects of EMF might not have been detected. However, this did not occur in our study; the only symptom with such data in the IEI-EMF group was “cold sweat,” and the number of participants in the IEI-EMF group with the provocation-positive/sham-negative status was also 0. Nevertheless, the number of participants in this study might not be sufficiently large to detect much rarer symptoms or smaller changes in physiological parameters. Furthermore, a washout period of 30 min might not be sufficiently long for some individuals with IEI-EMF, although we found no associations between the symptoms reported before the washout period and their existence during that the washout period.
In addition to conducting the provocation tests in a shielded laboratory and applying a high EMF exposure dose, this study had the advantage of a large sample size. Among the 12 previous studies assessed in the literature review, only one  included more participants with IEI-EMF (two more) than that in our study; moreover, our study included 32 more controls compared with this previous study. In addition, we collected information on both subjective symptoms and objective physiological parameters. Nevertheless, further studies are warranted to confirm our study findings, particularly the differences in physiological parameters between participants with IEI-EMF and controls when they perceived EMF exposure, which may provide insights into the etiology of IEI-EMF.