Acute cell phone exposure appears to increase glucose metabolism, a marker of neuronal activity, in the region of the brain adjacent to the device’s antenna, according to a report in the Feb. 23 issue of JAMA.
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Cell phone exposure appears to increase glucose metabolism in the region of the brain adjacent to the device’s antenna, according to a new report.
This brain region received the highest amplitude of radiofrequency-modulated electromagnetic fields (RF-EMFs) from the model of cell phone used in this study, given its position relative to the head during use. The finding suggests that brain absorption of RF-EMF energy emitted by cell phones "may enhance the excitability of brain tissue," wrote Dr. Nora D. Volkow, director of the National Institute on Drug Abuse, and her associates.
They studied brain glucose metabolism in 47 healthy volunteers using PET imaging with the injection of fluorodeoxyglucose-18. The volunteers wore devices that held cell phones in place simultaneously over both ears. As a part of the study’s randomized, crossover design, the investigators scanned the individuals on separate days, once with one cell phone activated but the sound turned off (the "on" condition) and once with both cell phones deactivated (the "off" condition).
Both ears were used "to avoid confounding effects from the expectation of a signal from the side of the brain at which the cell phone was located," the researchers explained.
After 50 minutes of exposure to radiation emitted during the on condition, there was a significant 7% increase in glucose metabolism (35.7 micromol/100 g per minute), compared with the off condition (33.3 micromol/100 g per minute). This occurred only in the right orbitofrontal cortex and the lower part of the right superior temporal gyrus – areas that corresponded to the location of the cell phone antenna.
Moreover, there was a linear relation between cell phone–related increases in metabolism and the estimated rate of radiofrequency energy absorption expected in various brain regions.
A 7% rise in regional metabolism is similar in magnitude to that reported after suprathreshold transcranial magnetic stimulation of the sensorimotor cortex, the investigators noted.
"These results provide evidence that the human brain is sensitive to the effects of RF-EMFs from acute cell phone exposures," Dr. Volkow and her colleagues wrote (JAMA 2011;305:808-14).
The clinical significance of the findings is not yet known. "The question that remains to be studied into the future is 'Could there be potential long-term consequences from repeated stimulation?'" Dr. Volkow said in a press teleconference. "The fact that we are observing changes really highlights the needs to do the studies to be properly able to answer the question of whether cell phone exposure could have harmful effects or not."
Although no safety risk can be inferred from the study, Dr. Volkow recommended that cell phone users who wish to take a conservative approach should use their phone in speaker phone mode or use a hands-free device, particularly for children, whose developing brains could be more at risk from RF activation and are likely to have many more years of cell phone use ahead of them.
The orbitofrontal cortex (OFC) helps to reinforce behaviors according to their context, such that hunger increases the value of food much more than when we are satiated, Dr. Volkow explained. If this area of the brain is damaged in animals, they will eat compulsively.
The OFC is also involved in social behaviors. Dr. Volkow noted the case of the 19th century railroad worker Phineas Gage, whose OFC was destroyed in an accident. Gage had been a very responsible man prior to the accident, but afterward the became completely unreliable and spent part of his life in prison, even though his intellectual abilities had not been disrupted.
However, Dr. Volkow noted that the areas of the brain that absorb RF energy will depend on the location of antenna in the cell phone and how it is held. The cell phone used in the current study was activated on the subject's right side and contained an antenna in the lower part of the phone near the receiver, thereby directing RF energy to the right OFC and lower part of the right superior temporal gyrus.
Previous PET imaging studies of cell phone use have been substantially smaller – the largest having 14 subjects – and may not have had the statistical power to detect small, but significant, signals. Those studies also measured brain activation via cerebral blood flow rather than the more sensitive method of measuring brain glucose metabolism.