During the second week of February, two meta-analyses that examined the research on the risk of cell phone use and brain tumor risk were published in peer-reviewed journals. Both papers reported a statistically significant relationship between cell phone use of ten or more years and increased brain tumor risk.
The authors of the first paper conclude that, "These results are in concordance with the conclusion of the expert panel for the International Agency for Research on Cancer (IARC), that cell phones are possibly carcinogenic (Group 2B)." The authors of the second paper call for the adoption of precautionary measures to reduce the adverse effects of cell phone use.
The first paper was published in the International Journal of Occupational Medicine and Environmental Health, and the second paper was published in the medical journal, Neurological Sciences.
The first study conducted by scientists at the Nofer Institute of Occupational Medicine, in Łódź, Poland, examined the research on mobile phone use and the risk of brain tumors and salivary gland tumors. The study found a significant relationship between mobile phone use and the risk of an intracranial tumor on the same side of the head where the phone was placed during calls. The study also reported a significant relationship between mobile phone use of 10 or more years and intracranial tumor risk.
Mobile phone use and risk for intracranial tumors and salivary gland tumors
- A meta-analysis
Bortkiewicz A, Gadzicka E, Szymczak W. Mobile phone use and risk for intracranial tumors and salivary gland tumors - A meta-analysis. Int J Occup Med Environ Health. 2017 Feb 21;30(1):27-43. doi: 10.13075/ijomeh.1896.00802. Epub 2017 Feb 13.
Results of epidemiological studies on the association between use of mobile phone and brain cancer are ambiguous, as well as the results of 5 meta-analysis studies published to date. Since the last meta-analysis (2009), new case-control studies have been published, which theoretically could affect the conclusions on this relationship. Therefore, we decided to perform a new meta-analysis. We conducted a systematic review of multiple electronic data bases for relevant publications. The inclusion criteria were: original papers, case-control studies, published till the end of March 2014, measures of association (point estimates as odds ratio and confidence interval of the effect measured), data on individual exposure. Twenty four studies (26 846 cases, 50 013 controls) were included into the meta-analysis. A significantly higher risk of an intracranial tumor (all types) was noted for the period of mobile phone use over 10 years (odds ratio (OR) = 1.324, 95% confidence interval (CI): 1.028-1.704), and for the ipsilateral location (OR = 1.249, 95% CI: 1.022-1.526). The results support the hypothesis that long-term use of mobile phone increases risk of intracranial tumors, especially in the case of ipsilateral exposure. Further studies are needed to confirm this relationship.
The results obtained in the random effects model indicated that there was a significant relationship between mobile phone use for longer than 10 years and the risk of intracranial tumors (OR = 1.46, 95% CI: 1.07–1.98).
Because OR is significantly greater than 1 (OR = 1.25, 95% CI: 1.04–1.52), we can conclude that there is a significant relationship between the time from the first regular use of mobile phone of 10 years or more and the risk of intracranial tumors.
Since OR is greater than 1 (OR = 1.29, 95% CI: 1.06–1.57), there is a significant relationship between ipsilateral use of mobile phone and the risk of intracranial tumor.
We found a significant relationship between:
–– all intracranial tumors and all phone types; ipsilateral exposure;
–– all intracranial tumors and all phone types, when the time of mobile phone use was not shorter than 10 years;
–– all intracranial tumors and all phone types when the time from the first regular use of mobile phone was 10 years or more.
We are not able to compare our results with reference to different kinds of intracranial tumors (glioma, meningioma, acoustic neuroma) in relation to time of using mobile phones. A reliable analysis was not feasible because, in our opinion, the number of original works is too small.
Our results support the hypothesis that long-term (over 10 years) use of mobile phones increases the risk of intracranial tumors, especially in the case of ipsilateral exposure. The same conclusions are valid for the work by Davis et al. (2013) , who reviewed papers on the association between the use of wireless (mobile and cordless) phones and intracranial tumors. Those authors stress that the risk of tumors in people who have used the phone for periods longer than 10 years is significantly elevated. In people who had started using the phone on a regular basis before they were 20 years old, the risk of ipsilateral glioma was found to be fourfold higher. Hardell et al. (2013)  stress the significance of the “lifetime exposure dose.” For an exposure of ≥ 1640 h, the risk of ipsilateral acoustic neuroma is 2.55 (95% CI: 1.5–4.4).
These results are in concordance with the conclusion of the expert panel for the International Agency for Research on Cancer (IARC), that cell phones are possibly carcinogenic (Group 2B) . More research is needed to confirm that electromagnetic fields emitted by mobile phones are carcinogenic to humans.
Open Access Paper: http://bit.ly/2m8Amwt
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.
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.
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.
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.
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.