Meta-analyses of studies on the association between electromagnetic fields and childhood cancer.

Radiation and environmental biophysics · 1996 · Mixed · Low evidence

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MixedLow evidencePaper 5414

Study snapshot

PublicationRadiation and environmental biophysics · 1996

Study typemeta_analysis

Reported directionMixed

Evidence ratingLow

Abstract

During the last 15 years several studies have investigated a possible relationship between exposure to electromagnetic fields (EMF) and childhood cancer. There is considerable variation between these studies with respect to methods of exposure assessment and reported results. Methods of exposure assessment range from simple visual criteria to costly and time consuming measurements or estimations of electric flux density. Additional individual refinements further hinder the comparability of results. We carried out several meta-analyses of data published so far taking into account the heterogeneity between studies as far as possible. Our particular interest was to investigate a potential dose-response-like relationship by comparing analyses for different cut-off points of exposure. Our meta-analyses suggest a marginal association between all cancer diagnoses combined and EMF exposure assessed by the two-level wire code (odds ratio, OR = 1.37, 95% confidence interval, CI: 0.94-2.00). Based on this criterion a significant effect was found for bases of leukemia (OR = 1.66, CI: 1.11-2.49) but not for central nervous system (CNS) tumors (OR = 1.5, CI: 0.69-3.26) or lymphomas (OR = 1.32, CI: 0.52-3.37). A significant increase in overall cancer risk with increasing stages of the four-level wire code (P = 0.003) could not be confirmed when data of the initial study performed by Wertheimer and Leeper were excluded (P = 0.17). When the exposure criterion was based on distance to the transmission line, estimated ORs for all cancers combined and for leukemias increased with distances decreasing from 100 to 25 m. Those analyses incorporating data on measured or calculated EMFs demonstrated also an increase of overall cancer risk with higher cut-off points. However, regarding individual diagnoses, this finding was reflected only in the group of brain tumors. One possible explanation for the high degree of heterogeneity between studies--especially with respect to methods of exposure assessment and choice of the respective cutpoint relevant for an increase in cancer risk--could be that published cut-off points were not always chosen in advance, but were selected because in exploratory analyses the most striking results were obtained with these specific cut-off values. Should this speculation be true at least partially, any meta-analysis will yield a false-positive finding. Further results of comparable studies with strictly a priori planned analyses are necessary to properly investigate a possible link between EMF and childhood cancer.

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AI evidence extraction

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Study typemeta_analysis

Effect directionmixed

Populationchildren (childhood cancer)

Sample sizeNot supplied

ExposureNot supplied

Evidence strengthLowConfidence: 78% · Peer reviewed: yes

Main findings

Meta-analyses of published studies suggested a marginal association between all childhood cancers combined and EMF exposure assessed by two-level wire code (OR 1.37, 95% CI 0.94–2.00). A significant association was reported for leukemia using this criterion (OR 1.66, 95% CI 1.11–2.49), but not for CNS tumors or lymphomas. Dose-response-like patterns were inconsistently supported: a significant trend across four-level wire code stages was not confirmed after excluding the initial Wertheimer and Leeper study, while analyses using distance to transmission lines and measured/calculated EMFs showed increasing overall cancer risk with higher exposure cut-offs, with individual-diagnosis patterns mainly reflected for brain tumors.

Outcomes measured

childhood cancer (all diagnoses combined)
leukemia
central nervous system (CNS) tumors
lymphomas
brain tumors

Limitations

Considerable heterogeneity between included studies, especially in exposure assessment methods and cut-off points.
Comparability of results hindered by differing exposure metrics (visual criteria, measurements, estimations of electric flux density) and additional refinements.
Dose-response trend across four-level wire code not robust to exclusion of the initial Wertheimer and Leeper study.
Potential for false-positive findings if exposure cut-off points were selected post hoc based on exploratory analyses.
Authors note need for further comparable studies with strictly a priori planned analyses.

View raw extracted JSON

{
  "study_type": "meta_analysis",
  "exposure": {
    "band": null,
    "source": null,
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": "children (childhood cancer)",
  "sample_size": null,
  "outcomes": [
    "childhood cancer (all diagnoses combined)",
    "leukemia",
    "central nervous system (CNS) tumors",
    "lymphomas",
    "brain tumors"
  ],
  "main_findings": "Meta-analyses of published studies suggested a marginal association between all childhood cancers combined and EMF exposure assessed by two-level wire code (OR 1.37, 95% CI 0.94–2.00). A significant association was reported for leukemia using this criterion (OR 1.66, 95% CI 1.11–2.49), but not for CNS tumors or lymphomas. Dose-response-like patterns were inconsistently supported: a significant trend across four-level wire code stages was not confirmed after excluding the initial Wertheimer and Leeper study, while analyses using distance to transmission lines and measured/calculated EMFs showed increasing overall cancer risk with higher exposure cut-offs, with individual-diagnosis patterns mainly reflected for brain tumors.",
  "effect_direction": "mixed",
  "limitations": [
    "Considerable heterogeneity between included studies, especially in exposure assessment methods and cut-off points.",
    "Comparability of results hindered by differing exposure metrics (visual criteria, measurements, estimations of electric flux density) and additional refinements.",
    "Dose-response trend across four-level wire code not robust to exclusion of the initial Wertheimer and Leeper study.",
    "Potential for false-positive findings if exposure cut-off points were selected post hoc based on exploratory analyses.",
    "Authors note need for further comparable studies with strictly a priori planned analyses."
  ],
  "evidence_strength": "low",
  "confidence": 0.78,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "electromagnetic fields",
    "EMF",
    "childhood cancer",
    "leukemia",
    "brain tumors",
    "CNS tumors",
    "lymphoma",
    "wire code",
    "transmission line distance",
    "meta-analysis",
    "dose-response",
    "exposure assessment"
  ],
  "suggested_hubs": [
    {
      "slug": "who-icnirp",
      "weight": 0.35,
      "reason": "Addresses EMF exposure and cancer risk, a topic commonly covered in major health risk assessments and guidelines."
    },
    {
      "slug": "occupational-exposure",
      "weight": 0,
      "reason": null
    }
  ]
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1007/bf01211237
PubMed: 8907639

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