Authors:
Myung SK, Ju W, McDonnell DD, Lee YJ, Kazinets G, Cheng CT, Moskowitz JM. Mobile phone use and risk of tumors: A meta-analysis. J Clin Oncol. Ahead of print Oct 13, 2009.

Background
As the use of mobile phones has increased, so have concerns about the potential carcinogenic effects of exposure to radiofrequency electromagnetic fields (EMFs) emitted from these devices.  Some of the studies not conducted in living organisms (‘in vitro’ studies) report that high-frequency EMFs increase cell proliferation and activation of genes involved in tumor formation.  Nonetheless, the effect of EMF on the incidence of cancer in humans remains unclear.

Objective
The objective of this study was to systematically investigate the evidence from case-control studies on the association between mobile phone use and the risk of tumors, including both malignant and benign conditions.

Methods
Databases were searched for studies published between 1968 and 2008, and all case-control studies that looked at the association between cellular or cordless phone use and malignant or benign tumors were included.  The overall risk of tumors was calculated based on meta-analysis of the results from the identified studies.

Results
Database searches returned 465 potential relevant articles, of which 23 case-control studies reported in 22 articles were included in the meta-analysis. The total number of cases and controls included in the analysis was 12,344 and 25,572 respectively. The mean age was 52.6 years (range 18-90 years) and 51% of the participants were women.  Among cases, 43.5% reported using a mobile phone, compared to 45.2% of controls.  When all 23 studies were considered, use of mobile phones (use vs. rarely or never use) was not significantly associated with the risk of tumors.  However, among 8 studies in which the interviewers were blind to the case-control status of participants (a way to minimize bias), a harmful effect of mobile phone use on tumor risk was observed.  When overall study quality was considered, studies of high methodological quality found a significant association between phone use and tumor risk, whereas those of low methodological found an inverse (protective) association between phone use and tumor risk.  In the 13 studies that reported risk between mobile phone use of 10 years or longer and tumor risk, a significant positive association was found. No association was found when analyses were restricted to brain tumors and other tumors separately.

Interpretation and Limitations
The use of mobile phones was associated with a mild increased risk of tumors, when compared with never or rare use of mobile phones, in a meta-analysis of case-control studies that used blinding or had a high methodological quality, whereas no significant association was observed in the meta-analysis of all included studies.  The findings were strongly related to the fact that all studies by one research group used blinding and had high methodological quality and found a positive association.  Recall and selection bias may have accounted for the inverse association observed in many of the studies conducted by another large research group (the INTERPHONE studies).
Conclusions
This meta-analysis of case-control studies found evidence linking mobile phone use to an increased risk of tumors, especially among users of 10 or more years. These findings should be confirmed in prospective cohort studies.

 

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