Less than one hour on the cellphone has been shown to significantly increase brain activity, especially in the area closest to the phone’s antenna. Is this good or bad? In a study just published in the Journal of the American Medical Association, researchers from the National Institutes of Health in Bethesda, MD and Brookhaven National Laboratories in Upton, NY presented convincing evidence of this localized increase, but could not say whether the findings may have any clinical significance. At issue was whether exposure to cell phone radiofrequency signals has any noticeable and, most importantly, any dangerous effects on the human brain.
One of the measures that best indicates brain activity levels is brain glucose metabolism. In a randomized crossover study conducted between January 1 and December 31, 2009, at Brookhaven National Laboratory, 47 healthy individuals were asked to use their cell phone during a period of 50 minutes. Using positron emission tomography (a PET scan) to detect levels of the biological marker 18F-fluorodeoxyglucose, brain glucose metabolism was measured with the cell phone activated (sound muted) for 50 minutes (switch in the “on” position) and with the cell phone deactivated (“off” position). Statistical tools were used to compare brain glucose metabolism between on and off conditions, and to verify the association of brain glucose metabolism and the estimated amplitude of radiofrequency-modulated electromagnetic waves emitted by the cell phones.
The results of the tests indicate that glucose metabolism throughout the whole brain did not differ between on and off conditions. However, glucose metabolism in the region of the brain closest to the cell phone antenna (corresponding to the orbitofrontal cortex and the temporal area) was significantly higher when the phone was on (35.7 vs. 33.3 μmol/100g per minute). The increase in brain activity appeared to be directly correlated with the estimated electromagnetic field amplitudes.
The researchers conclude that, compared with no exposure at all, a 50-minute cell phone conversation is associated with increased brain glucose metabolism in the region closest to the antenna. Short of any evidence that this increase is harmful, the study authors concluded that this finding “is of unknown clinical significance.”
What Is Brain Glucose Metabolism?
Brain glucose metabolism is the use of glucose (sugars) to create energy for neural activation, as the brain requires a continuous supply of glucose carried to it by blood circulation to meet its metabolic requirements. The central nervous system is dependent upon a continuous supply of blood and the viability of brain cells depends upon the immediate and constant availability of oxygen and glucose.
Although there is inconsistent evidence that increased brain glucose metabolism is pathogenic, the consensus is that it may be a contributing factor in causing a higher than normal concentration of extracellular potassium (ionic disequilibrium), that it may produce fluctuating levels of extracellular excitatory amino acids, and that it may be responsible for localized brain seizure activity.
Similar to the detrimental effects of too little glucose (hypoglycemia), periods of too high glucose (hyperglycemia) have been shown to worsen neurologic outcomes, i.e., to aggravate any existing brain disorder. More specifically, high glucose can cause isolated seizures and situation-related syndromes, such as fever seizures and seizures due to alcohol, drugs, or complications of pregnancy. In fact, longitudinal neuroimaging studies of alcohol-dependent individuals have revealed increased brain glucose metabolism in the frontal cortex and other studies have revealed that cocaine at doses typically used by drug abusers also significantly increased brain glucose metabolism.
Scans of amphetamine users have shown a 14% increase in whole brain metabolism in abusers as compared to non-abusers. Differences were most accentuated in the parietal cortex, an area of the brain that regulates sensation and coordinates information on space and spatial relations. "This finding was a complete surprise," study author Dr. Volkow says. "Most drug studies have shown decreased metabolism. The increased metabolism we saw is consistent with an inflammatory response. This result, taken together with our other findings, indicates that this is a very toxic drug." The presence of inflammation signals that there is a physical injury to the brain.
While it is premature to conclude that cell phone use is harmful to the human brain, the concern has been around for a while and the possible correlation between electromagnetic waves and brain injuries continues to be studied. That a direct correlation of higher than normal brain activity and cell phone use has been so clearly established may however be sufficient to give many of us a reason for using text messaging and a plain old landline to reach out and touch someone.