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Cell Phone Activation and Brain Glucose Metabolism

Cell Phone Activation and Brain Glucose Metabolism To the Editor: The investigation by Dr Volkow and colleagues1 found evidence for increased brain metabolic activity due to cell phone radiation exposure. A number of aspects of the study call the results into question. First, the physics of radiation used in the analysis is overly simplified. The authors assumed that the radiofrequency-modulated electromagnetic fields (RF-EMFs) deposited in the brain had an amplitude equal to the electric field of a near-field dipole in a vacuum. Cell phone antennas are often fractal instead of dipole, significant angular dependence is ignored, and the brain has complicated dielectric properties, which may lead to large differences from the assumed field and invalidate the claimed correlation. Electromagnetic fields in tissue have been studied extensively2 and a more realistic model is possible. The study also did not control for possible effects of simple thermal heating from the active cell phone. Second, although the participants were blinded to condition, the researchers performing the analysis were not. The statistics used relied explicitly on knowing which brain images were performed with active cell phones, making biases more likely. The study also did not randomize the side of the head on which the active cell phone was placed. Third, the statistical results do not appear internally consistent. Figure 3 shows a nearly constant difference in brain activity between clusters with the cell phone on and off. The plot has no error bars, but the errors must be small compared with the difference to demonstrate such a regular pattern. This suggests an extremely significant effect, contradicting the authors' claim of an effect at only somewhat above the 95% confidence level. The other panels of this plot show a tight linear relation with error bars that must either be greatly overestimated or highly correlated. Finally, the striking feature of the brain images shown in Figure 2 is that the scan with the cell phone on shows a much higher overall level of brain activity, contrasting with the authors' statement that whole-brain glucose metabolism did not differ between conditions. On the other hand, the difference between right and left appears similar in the on and off conditions except with the sides reversed, suggesting differences may be due to noise. Back to top Article Information Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported. References 1. Volkow ND, Tomasi D, Wang G-J, et al. Effects of cell phone radiofrequency signal exposure on brain glucose metabolism. JAMA. 2011;305(8):808-81321343580PubMedGoogle ScholarCrossref 2. Barnes F, ed, Greenebaum B, ed. CRC Handbook of Biological Effects of Electromagnetic Fields. 3rd ed. Boca Raton, FL: CRC Press; 2006 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png JAMA American Medical Association

Cell Phone Activation and Brain Glucose Metabolism

JAMA , Volume 305 (20) – May 25, 2011

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Publisher
American Medical Association
Copyright
Copyright © 2011 American Medical Association. All Rights Reserved.
ISSN
0098-7484
eISSN
1538-3598
DOI
10.1001/jama.2011.669
Publisher site
See Article on Publisher Site

Abstract

To the Editor: The investigation by Dr Volkow and colleagues1 found evidence for increased brain metabolic activity due to cell phone radiation exposure. A number of aspects of the study call the results into question. First, the physics of radiation used in the analysis is overly simplified. The authors assumed that the radiofrequency-modulated electromagnetic fields (RF-EMFs) deposited in the brain had an amplitude equal to the electric field of a near-field dipole in a vacuum. Cell phone antennas are often fractal instead of dipole, significant angular dependence is ignored, and the brain has complicated dielectric properties, which may lead to large differences from the assumed field and invalidate the claimed correlation. Electromagnetic fields in tissue have been studied extensively2 and a more realistic model is possible. The study also did not control for possible effects of simple thermal heating from the active cell phone. Second, although the participants were blinded to condition, the researchers performing the analysis were not. The statistics used relied explicitly on knowing which brain images were performed with active cell phones, making biases more likely. The study also did not randomize the side of the head on which the active cell phone was placed. Third, the statistical results do not appear internally consistent. Figure 3 shows a nearly constant difference in brain activity between clusters with the cell phone on and off. The plot has no error bars, but the errors must be small compared with the difference to demonstrate such a regular pattern. This suggests an extremely significant effect, contradicting the authors' claim of an effect at only somewhat above the 95% confidence level. The other panels of this plot show a tight linear relation with error bars that must either be greatly overestimated or highly correlated. Finally, the striking feature of the brain images shown in Figure 2 is that the scan with the cell phone on shows a much higher overall level of brain activity, contrasting with the authors' statement that whole-brain glucose metabolism did not differ between conditions. On the other hand, the difference between right and left appears similar in the on and off conditions except with the sides reversed, suggesting differences may be due to noise. Back to top Article Information Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported. References 1. Volkow ND, Tomasi D, Wang G-J, et al. Effects of cell phone radiofrequency signal exposure on brain glucose metabolism. JAMA. 2011;305(8):808-81321343580PubMedGoogle ScholarCrossref 2. Barnes F, ed, Greenebaum B, ed. CRC Handbook of Biological Effects of Electromagnetic Fields. 3rd ed. Boca Raton, FL: CRC Press; 2006

Journal

JAMAAmerican Medical Association

Published: May 25, 2011

References