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21 February 2017

Long-Term Cell Phone Use Increases Brain Tumor Risk

"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."

Long-term cell phone use increases brain tumor risk

Electromagnetic Radiation Safety, 20 February 2017

Mobile phone use and risk of brain tumors: a systematic review

The results of a newly published 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.

Overall, the study found that long-term or heavy cell phone use was associated with a 33% increased risk of a brain tumor.

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.

Based upon the results of this review, the authors recommend that precautionary measures be taken to reduce the adverse effects of cell phone use.

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.

This paper was published in the peer-reviewed medical journal, Neurological Sciences.

The first author of this paper, Dr. Manya Prasad is in the Department of Community Medicine, Postgraduate Institute of Medical Sciences, Rohtak. India. His colleagues are in the Department of Neurology, All India Institute of Medical Sciences in New Delhi, India.

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Mobile phone use and risk of brain tumours: a systematic review of association between study quality, source of funding, and research outcomes

Prasad M, Kathuria P, Nair P, Kumar A, Prasad K. Mobile phone use and risk of brain tumours: a systematic review of association between study quality, source of funding, and research outcomes. Neurological Sciences. 2017 Feb 17. doi: 10.1007/s10072-017-2850-8.

Abstract

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.

https://www.ncbi.nlm.nih.gov/pubmed/28213724

Excerpts

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.

The meta-analysis of case–control studies found that there is a significant positive correlation between study quality and risk of brain tumour associated with use of mobile phones. Higher quality studies show a statistically significant association between mobile phone use and risk of brain tumour, but adding poor quality studies leads to loss of significance. We found that Government funded studies were generally of higher methodological quality than phone industry funded or mixed funded.

However, one qualitatively similar finding in both government funded as well as mixed funded studies is that long-term use (10 or more years or 1640 or more hours of lifetime cellphone use) is associated with increased risk of brain tumour.

Conclusion

In our review of the literature and meta-analysis of case–control studies, we found evidence linking mobile phone use and risk of brain tumours especially in long-term users (greater than 10 years). We also found a significantly positive correlation between study quality and outcome in the form of risk of brain tumour associated with use of mobile phones. Higher quality studies show a statistically significant association between mobile phone use and risk of brain tumour. Even the source of funding was found to affect the quality of results produced by the studies. As mobile phone use certainly continues, our findings are pertinent to warrant application of precautionary measures aimed at reducing its adverse effects. Furthermore, well-designed studies embedded with prospective cohorts are required to provide a higher level of evidence.




More information about cell phone use and brain tumor risk
Brain Tumor Rates Are Rising in the US: The Role of Cellphone & Cordless Phone Use
The Incidence of Meningioma, a Non-Malignant Brain Tumor, is Increasing in the U.S.
Why do many scientists believe mobile phone use increases cancer risk?
MOBI-KIDS: Childhood Brain Tumor Risk & Mobile Phone Use Study
Wall Street Journal asks "Should Cellphones Have Warning Labels?"
Key Cell Phone Radiation Research Studies


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