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ABSTRACT & COMMENTARY
By Seema Gupta, MD, MSPH
Primary Care Physician, Charleston, WV
Dr. Gupta reports no financial relationships relevant to this field of study.
SYNOPSIS: In a pooled analysis of two case-control studies, mobile and cordless phone use increased the risk of glioma and that risk increased significantly with years and hours of use.
SOURCE: Hardell L, et al. Mobile phone and cordless phone use and the risk for glioma — Analysis of pooled case-control studies in Sweden, 1997-2003 and 2007-2009. Pathophysiology 2014 Oct 29. pii: S0928-4680(14)00064-9. doi: 10.1016/j.pathophys.2014.10.001. [Epub ahead of print].
In the past decade, cellular phone usage has grown exponentially worldwide, and this use is prevalent in all age groups, including children. Currently, more than 90% of the populations in the United States and Western Europe utilize this mode of wireless communication. This has raised concerns for health risks due to a greater exposure to radiofrequency electromagnetic fields. These radiations are considered non-ionizing, meaning that they do not have sufficient energy to break off electrons from their orbits around atoms and ionize the atoms, such as ionizing radiations. Previous studies have suggested that these radiofrequency signals emanating from cellular phones, cordless phones, and other devices may have biologic effects on target cells or tissues.1,2 Brain tissue is the main target of such radiation exposure, especially on the side of the brain where the mobile device is regularly used. The brain tumors associated with the use of cellular phones are the malignant types, mostly glioma, and a benign tumor, acoustic neuroma.3 In contrast, no consistent pattern of an association has been found for the most common benign brain tumor, meningioma. With the average age to begin cell phone use declining in the recent years, children may be at particular risk owing to the duration of exposure to radiations as well as the potential to absorb at higher rates due to high conductivity as a result of smaller head size and thinner skull bones. Long-term use data provide an opportunity to conduct more detailed analysis on the relationship between such radiation exposure and the risk for the development of brain tumors.
In their study, Hardell et al conducted a pooled analysis of two Swedish case-control studies on malignant brain tumors with patients diagnosed during 1997–2003 and 2007-2009 from six administrative regions with oncology centers covering newly registered cancer cases in Sweden. The trial included both men and women ages 20-80 years (1997-2003) and 18-75 years (2007-2009) at the time of diagnosis. Only cases with histopathological verification of the tumor were included. Exposure was assessed using a mailed questionnaire for each participant. Overall, 1498 (89%) cases and 3530 (87%) controls participated in the study.
Researchers found that an increased risk for glioma was associated with use of both cellular and cordless phones, and that risk increased significantly with years and hours of use. Study participants who talked on cellular phones for more than 25 years had a statistically significant three-fold increased risk (odds ratio [OR] = 3.0; 95% confidence interval [CI] = 1.7–5.2) compared to those who used wireless phones for less than a year. Overall, the use of cellular phone increased the risk of glioma (OR = 1.3; 95% CI = 1.1-1.6). Similarly, in cordless phone users, there was an increase in risk (OR = 1.4; 95% CI = 1.1-1.7), with the highest risk in the > 15–20 years latency group (OR = 1.7; 95% CI = 1.1–2.5). The odds ratio increase was found to be statistically significant for both per 100 hours of cumulative use and per year of latency for cellular and cordless phone use. The researchers found the highest odds ratio for ipsilateral cellular or cordless phone use (OR = 1.8; 95% CI = 1.4-2.2 and OR = 1.7; 95% CI = 1.3-2.1, respectively). Most of the types of malignant brain tumors were glioma (n = 1380; 92.1%) with the most malignant variety, astrocytoma grade IV (glioblastoma multiforme) comprising 50.3% of such gliomas.
The authors have found additional evidence suggesting a possible association between brain tumors and wireless phone devices. This could be possibly explained by the electromagnetic fields disrupting the ability of brain cells to repair the damaged DNA or potentially causing gene mutations. However, we should be careful in noting that an association does not automatically equate to causation. The carcinogenic effect of radiofrequency electromagnetic field on humans was evaluated by a panel of scientists at the World Health Organization’s (WHO) International Agency for Research on Cancer in 2011.4 The Working Group categorized these non-ionizing radiations being emitted from mobile phones and other devices as a Group 2B (i.e., a “possible carcinogen” in humans). However, it is significant to note that not all studies thus far have demonstrated a consistent link between cell phone use and cancers of the brain. The INTERPHONE study group found that there was no increase in risk of acoustic neuroma with the regular use of a mobile phone or for users who began regular use 10 years or more before the reference date.5 The National Cancer Institute’s position is that there has not been a consistent link demonstrated between cell phone use and cancers of the brain, nerves, or other tissues of the head or neck. It is clear that further research is needed to establish whether there is a cause and effect relationship between radiations emitted by wireless devices and brain tumors. The best advice to our patients presently may be to disclose that such radiations are considered a possible carcinogen by the WHO and further research is ongoing. However, for children, it may be pertinent to recommend avoiding excess contact with such devices such as sleeping with their cellular phone under the pillow.