Cell Phone Radiofrequency Exposure Alters Brain Glucose Metabolism

S. Andrew Josephson, MD; AccessMedicine from McGraw-Hill © 2011 The McGraw-Hill Companies

Cellular telephone use has become quite common worldwide. A number of concerns have been raised regarding whether exposure to radiofrequency-modulated electromagnetic fields (RF-EMFs) emitted by cellular phones can lead to an increased rate of cancer, although epidemiologic studies have failed to prove this increased carcinogenic risk. These RF-EMFs could also, in theory, influence neuronal activity in the brain, and a recent study by Volkow and colleagues (2011) elegantly attempted to study whether changes in regional brain activity could be observed with cellular phone use.

The authors recruited 48 healthy volunteers who did not abuse illicit drugs, alcohol, or nicotine. All of the participants agreed to undergo 2 positron emission tomography (PET) scans on separate days to measure cerebral blood flow using fluorodeoxyglucose (18FDG) injection. Prior to each of the scans, participants had 2 cellular phones placed on their head (one over each ear). Each cellular phone was muted so that the participant did not know if it was turned on or receiving calls. On one of the days, both phones were turned off for the entire period, and on the other day, the right ear cellular phone was on throughout the experiment and receiving a muted call. The order of the conditions was randomly assigned, and participants were blinded to the experimental protocol and order. RF-EMF emissions were directly recorded using a handheld device in order to ensure that the phone was indeed on when intended, and cellular phone company records were examined to verify that a call was taking place.

Patients received the 18FDG injection 20 min after the beginning of the experiment, and the cell phones were removed 30 min later just prior to the scan. During the 50 min of the experiment, subjects sat quietly in a dimly lit room with their eyes open and cellular phones attached. The authors placed the phones on the head with antennae in a standard position, and in roughly half of the patients an additional photography analysis was used to note the position of the antennae in relationship to the brain.

While whole-brain glucose metabolism did not differ between the off and on conditions, there were significant regional differences demonstrated. There were increases in brain glucose metabolism noted in regions corresponding to the right orbitofrontal cortex and right superior temporal gyrus in the on compared with the off conditions (35.7 vs. 33.2 ┬Ámol/100 g per min; mean difference, 2.4; 95% confidence interval, 0.67–4.2; p = .004). Similar significant regional differences were seen when normalizing the images to whole-brain glucose metabolism. Areas of the brain with increased glucose metabolism corresponded to those regions expected to have the highest RF-EMF exposure given their proximity to the antennae of the turned-on cellular phone.

These results suggest that changes in excitability of brain tissue occur with exposure to RF-EMFs from cellular phones. A previous study by Ferreri (2006) suggested that EMF exposure from cellular phones acutely increased intracortical excitability when tested using transcranial magnetic stimulation (TMS) and recording motor evoked potentials. The mechanism responsible for these alterations in neuronal activity is unclear. Animal and in vitro studies have suggested that this RF-EMF exposure could affect neuronal activity through changes in membrane permeability, cellular excitability, or neurotransmitter release. It is unlikely that this observation is due exclusively to a thermal effect generated by the heat of the cellular phone given the lack of much diffusion of heat into the brain itself from the surface.

The clinical significance of the findings in this paper is completely unclear, and any short- or long-term consequences are purely speculative. However, cellular phone exposure does seem to affect brain function in terms of regional increases in metabolism in those areas with the highest exposure to RF-EMF. This study is intriguing, and given the widespread use of these devices, it should lead to further study of this effect, its mechanism, and potential clinical consequences.

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