Effectiveness of electromagnetically shielded rooms in hospitals or other health care institutions: a systematic review and meta-analysis of provocation studies
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Key message
Electromagnetic hypersensitivity refers to self-reported health problems triggered by exposure to electromagnetic fields such as base stations, mobile phones and/or visual display units. We wanted to assess effectiveness of electromagnetically shielded rooms in hospitals or other health care institutions, regardless of the cause for hospitalization. To support a possible benefit from such rooms, we also summarized research on electromagnetic hypersensitive persons’ ability to distinguish between exposure to electromagnetic fields and sham exposure.
- We found no studies investigating effects of electromagnetically shielded rooms in hospitals or other health care institutions. Therefore, we have no evidence to conclude on effectiveness of electromagnetically shielded rooms.
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Our meta-analysis suggested that:
- Sensitive persons’ ability to distinguish between exposure to weak electromagnetic fields and sham in blinded tests is the same as can be expected by chance.
- Sensitive persons’ ability to distinguish between exposure to weak electromagnetic fields and sham is the same as non-sensitive controls.
In the studies where subjects were asked to distinguish between exposure to weak electromagnetic fields and sham, they only explored exposure up to three hours. Therefore, we cannot rule out the possibility that prolonged exposure can provide different results.
Summary
Background
The Central Norway Regional Health Authority asked the Norwegian Knowledge Centre for the Health Services to summarize the research on effectiveness of electromagnetically shielded rooms in hospitals or other health care institutions, regardless of cause for hospitalization.
Electromagnetic hypersensitivity (also called idiopathic environmental intolerance attributed to electromagnetic fields IEI-EMF) refers to subjective health complaints that are perceived to be triggered by exposure to weak electromagnetic fields such as base stations, mobile phones and/or visual display units. Health problems include a variety of non-specific symptoms such as joint and muscle pain, headaches, vision problems, skin problems, sleep disturbances, depression, loss of concentration and poor memory.
We searched for studies on effectiveness of electromagnetically shielded patient rooms. To support a possible benefit of these rooms, we summarized research on whether sensitive persons can distinguish between exposure to electromagnetic fields and sham exposure, compared to what can be expected by chance and outcomes for people without electromagnetic hypersensitivity.
Method
The search strategy was developed based on the population and the intervention we wanted to investigate. Inclusion criteria were:
1. Effectiveness of electromagnetically shielded rooms in hospital or other health care institutions for electromagnetically hypersensitive people, regardless of cause for hospitalization.
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Study design: |
Randomized controlled trials |
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Population: |
Electromagnetically sensitive adults |
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Intervention: |
Shielding from electromagnetic fields (shielded room) |
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Comparison: |
No shielding from electromagnetic fields |
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Outcome : |
Subjective health symptoms |
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Language : |
English, Scandinavian |
2. Ability to distinguish between electromagnetic fields and sham exposure
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Study design: |
Randomized controlled trials |
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Population: |
Electromagnetically sensitive adults |
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Intervention: |
Exposure to weak electromagnetic fields |
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Comparison: |
Sham exposure or no exposure |
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Outcome : |
Ability to distinguish between electromagnetic fields and sham exposure |
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Language : |
English, Scandinavian |
We initially found one systematic review from 2005 with an update from 2010. In an updated search up to 2012, we used the search strategies from the systematic reviews. We searched the Cochrane Library, Center for Reviews and Dissemination (CRD), Ovid MEDLINE, EMBASE, PsycINFO, AMED, Cochrane Central Register of Controlled Trials (CENTRAL) and Ovid MEDLINE In-Process & Other Non-Indexed Citations in May/June 2011 and in January 2012. We supplemented the systematic search with a check of relevant reference lists and websites.
Two reviewers independently assessed studies for inclusion and for trial quality following the Knowledge Centre's handbook. Where necessary, authors were contacted for additional information. We summarized the results in text, tables and figures.
Results
We found 21 publications (with 22 experiments) that met our inclusion criteria, from 762 potentially relevant publications.
We found no studies that investigated the effect of electromagnetically shielded rooms in hospitals or health care institutions.
We included 21 publications, with 22 experiments, on exposure to weak electromagnetic fields compared to sham exposure. The studies included 1493 participants. We found a low risk of bias across the included studies. We performed meta-analyses of the ability to distinguish between weak electromagnetic fields and sham exposure in sensitive persons and non-sensitive control subjects, and compared this with what can be expected by chance. The meta-analysis included 16 experiments with electromagnetically hypersensitive persons and 10 experiments with non-sensitive control subjects.
Our meta-analysis suggested that:
- The ability of electromagnetically hypersensitive persons to distinguish between exposure to weak electromagnetic fields and sham exposure in blinded test situations as measured by event rate transformed to be centered at zero (0.02, 95 % CI -0.02 til 0.06) is the same as can be expected by chance
- Electromagnetically hypersensitive people cannot distinguish between exposure to weak electromagnetic fields and sham better than non-sensitive control subjects (Chi squared=3,10, df=1, p=0.08)
Discussion
The results of our systematic review are consistent with results from other systematic reviews in terms of ability to distinguish between weak exposure to electromagnetic fields and sham exposure. Limitations of the included studies are that they only explored exposure up to three hours. Therefore, we cannot rule out the possibility that prolonged exposure can provide different results.
Some persons with electromagnetic hypersensitivity claim that they know when they are exposed to electromagnetic fields, while others report that symptoms can arise some time after exposure. The experience of exposure does not necessarily mean that one gets health problems after exposure. Hence, both objective findings and self-reported symptoms can be weighted as part of a utility assessment of electromagnetically shielded rooms. Although objective findings and self-reported symptoms are not addressed in our systematic review, other researchers have explored these problems without finding associations.
Conclusion
Effectiveness of electromagnetically shielded rooms in hospital or health care institutions for electromagnetically hypersensitive people:
We found no studies on the effect of electromagnetically shielded rooms in hospitals or other health care institutions. Therefore, we have no evidence to conclude on effectiveness of electromagnetically shielded rooms.
Ability to distinguish between electromagnetic fields and sham exposure:
We found 22 experiments including 1493 participants with and without electromagnetic hypersensitivity that have assessed whether the subjects can differentiate between weak electromagnetic fields and sham in double-blind test situations. The experiments revealed that participants could state the presence of weak electromagnetic fields and sham in half of the test situations. This is the same as can be expected by chance.