Cell phone use alters brain glucose metabolism

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Lyndon McGill, D.C.

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Authors and Disclosures

S. phson, MD

Department of Neurology, University of California San

Francisco, San Francisco, USA

From AccessMedicine

from McGraw-Hill

Cell Phone Radiofrequency Exposure Alters Brain Glucose

Metabolism

S. phson, MD

Posted: 04/06/2011; 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

µmol/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.

References

Ferreri F et al. Mobile phone emissions and human

brain excitability. Ann Neurol 2006;60:188.

Volkow ND et al. Effects of cell phone

radiofrequency signal exposure on brain glucose

metabolism. JAMA 2011;305:808.

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