In the U.S. the lifetime risk of developing glioma, the most common brain cancer, is between 1 in 200 and 1 in 250. If glioma risk doubled after 20 years of cell phone use (as the research cited below suggests), the lifetime risk would be between 1 in 100 and 1 in 125.
Three reviews of the research on cell phone use and brain tumor risk have been published in peer-reviewed journals in 2017. Each of these studies reports a statistically significant relationship between cell phone use of ten or more years and brain tumor risk especially on the side of the head where the cell phone was predominantly placed during phone calls (i.e., ipsilateral use).
Bradford Hill Viewpoints from 1965 on Association or Causation
"The nine Bradford Hill viewpoints on association or causation regarding RF radiation and glioma risk seem to be fulfilled in this review.
Based on that we conclude that glioma is caused by RF radiation. Revision of current guidelines for exposure to RF radiation is needed."
Drawing upon several lines of research, the authors present a compelling argument for their conclusion that glioma is caused by radio frequency (RF) radiation. The paper recommends that the current guidelines for RF exposure must be revised to protect the population from exposure to low-intensity, non-thermal levels of radio frequency radiation.
Biological gradient: cumulative use of wireless phones increased the risk.
Plausibility: animal studies showed an increased incidence of glioma and malignant schwannoma in rats exposed to radiofrequency (RF) radiation. There is increased production of reactive oxygen species (ROS) from RF radiation.
Coherence: there is a change in the natural history of glioma and increasing incidence.
Mobile phone use and risk of brain tumors: a systematic review
The results of a review and meta-analysis of the research on cell phone use and brain tumor risk found that long-term or heavy cell phone use was associated with a statistically significant increased risk of brain tumors.
The risk of a brain tumor for long-term cell phone use varied depending upon the quality of the research study with higher quality studies tending to yield greater risk estimates (see Table below). For the five highest quality studies, the estimates ranged from a 21% increased risk to 2.6 times the risk of a non-cellphone user. For five lower quality studies. the estimates ranged from a 47% reduced risk to 5.1 times the risk of a non-cellphone user.
In this study, long-term cell phone use was defined as ten or more years. The highest quality studies scored 7 or 8 on a 10-point scale, and the lower quality studies scored 5 or 6.
Mobile phones emit electromagnetic radiations that are classified as possibly carcinogenic to humans. Evidence for increased risk for brain tumours accumulated in parallel by epidemiologic investigations remains controversial. This paper aims to investigate whether methodological quality of studies and source of funding can explain the variation in results.
PubMed and Cochrane CENTRAL searches were conducted from 1966 to December 2016, which was supplemented with relevant articles identified in the references. Twenty-two case control studies were included for systematic review.
Meta-analysis of 14 case-control studies showed practically no increase in risk of brain tumour [OR 1.03 (95% CI 0.92-1.14)]. However, for mobile phone use of 10 years or longer (or 1,640 or more hours in lifetime), the overall result of the meta-analysis showed a significant 1.33 times increase in risk. The summary estimate of government funded as well as phone industry funded studies showed 1.07 times increase in odds which was not significant, while mixed funded studies did not show any increase in risk of brain tumour. Meta-regression analysis indicated that the association was significantly associated with methodological study quality (p < 0.019, 95% CI 0.009-0.09). Relationship between source of funding and log OR for each study was not statistically significant (p < 0.32, 95% CI 0.036-0.010).
We found evidence linking mobile phone use and risk of brain tumours especially in long-term users (10 or more years). Studies with higher quality showed a trend towards high risk of brain tumour, while lower quality showed a trend towards lower risk/protection.
In the 22 case–control studies, a total of 48,452 participants (17,321 patient cases and 31,131 controls) were identified, with the mean age of 46.65 years (range 18–90 years). Data for ipsilateral use and temporal lobe location could not be retrieved from the papers. However, data for long-term use of mobile phones (10 or more years) were extracted from 12 studies out of 22 studies (Tables 1, 2).
Data from 14 case control studies were included in the meta-analysis. We identified a total of 30,421 participants (12,426 cases and 19,334 controls). In Fig. 2, the study with quality sum of 8 shows that there is 1.64 times increase in odds of having brain tumour with mobile phone use. In the hierarchical meta-analysis of studies with progressively lower quality scores of 7, 6, and 5, the odds ratio progressively decreased to 1.08, 0.98, and 0.81, respectively. Therefore, the overall result [OR 1.03 (95% CI 0.92–1.14)] shows a statistically insignificant increase in odds of risk of brain tumour.
In Fig. 3, the study with quality sum of eight shows that there is 2.58 times increase in odds of having brain tumour with mobile phone use of more than 10 years duration. In the meta-analysis, studies with progressively lower quality score of 7 and 6 show a progressively lower risk of brain tumour with odds ratio 1.44 and 1.13, respectively. However, the overall result of the meta-analysis shows a significant 1.33 times increase in odds of having risk of brain tumours with mobile phone use.
Stratified meta-analysis according to sources of funding shows a consistent increase in risk of brain tumour with mobile phone use of more than 10 years. While summary estimate of government funded studies shows 1.64 times increase in odds (Supplementary Figure IV), mixed funded studies show 1.05 times increase in odds of risk of brain tumours, but the results were not statistically significant (Supplementary Figure V). The data for more than 10 years of use were not available for phone industry funded studies.
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