24 February 2011
Cell phones do affect brain, but consequences unknown
by Kate Melville
Researchers have found that cell phone use is associated with increased brain glucose metabolism (an indicator of brain activity) in the region closest to the antenna, but they say that the finding is of unknown clinical significance.
The research, appearing in the Journal of the American Medical Asociation, notes that past studies of the association between cell phone use and prevalence of brain tumors have been inconsistent (some, but not all, studies showed increased risk). The researchers add that studies performed in humans to investigate the effects of radiofrequency-modulated electromagnetic field (RF-EMF) exposures from cell phones have yielded variable results, highlighting the need for studies to document whether RF-EMFs from cell phone use affects brain function in humans.
The new study, conducted by Nora D. Volkow, of the National Institutes of Health, included 47 participants. Cell phones were placed on the left and right ears of the subjects and brain imaging was performed with positron emission tomography twice, once with the right cell phone activated (sound muted) for 50 minutes ("on" condition) and once with both cell phones deactivated ("off" condition). Analysis was conducted to verify the association of brain metabolism and the amplitude of radiofrequency-modulated electromagnetic waves emitted by the cell phone.
Volkow found that whole-brain metabolism did not differ between the on and off conditions. However, there were significant regional effects. Metabolism in the brain region closest to the antenna (orbitofrontal cortex and temporal pole) was significantly higher (7 percent) for cell phone on than for cell phone off conditions. "The increases were significantly correlated with the estimated electromagnetic field amplitudes both for absolute metabolism and normalized metabolism," the study reports. "This indicates that the regions expected to have the greater absorption of RF-EMFs from the cell phone exposure were the ones that showed the larger increases in glucose metabolism."
"These results provide evidence that the human brain is sensitive to the effects of RF-EMFs from acute cell phone exposures," Volkow says. But she adds that the mechanisms by which RF-EMFs could affect brain glucose metabolism are unclear.
In an accompanying editorial, Henry Lai, of the University of Washington, said the results warrant further investigation. "An important question is whether glucose metabolism in the brain would be chronically increased from regular use of a wireless phone with higher radiofrequency energy than those used in the current study. Potential acute and chronic health effects need to be clarified." The editorial also questions whether the findings may be a marker of other alterations in brain function from radiofrequency emissions, such as neurotransmitter and neurochemical activities.
Source: Journal of the American Medical Asociation