By Mary Brophy Marcus, USA TODAY
Whether the increased sensitivity is harmless or hurtful to the brain is still up for debate, say researchers from the National Institutes of Health, who found that less than an hour of cellphone use is linked with increased activity in the part of the brain closest to the phone antenna.
It's not clear yet whether the radiation is potentially carcinogenic or has any other negative health implications — or positive ones, for that matter, says lead author Nora Volkow, director of the National Institute on Drug Abuse, about the research in this week'sJournal of the American Medical Association.
The year-long study on 47 people used positron emission tomography (PET) scans — a technique used to map out the brain. Study subjects underwent two injections with a dye that measures brain glucose metabolism, which is an indication of the brain's activity.
The first time around, cellphones were placed on both sides of the head. In half of the participants, the cellphone against the right ear was turned on with the sound muted for 50 minutes and in the other grooup, neither phone was activated. On the second test, the two groups were switched. None of the participants knew which phone was turned on.
The scientists found that metabolism in the brain region closest to the antenna — in the orbitofrontal cortex and temporal pole — was about 7% higher when the cellphone was on. The orbitofrontal cortex of the brain — one of the two areas that lit up on the scans — isn't linked to a single function, says Murali Doraiswamy, head of biological psychiatry at Duke Medical Center, who wasn't involved in the study. "It's broadly associated with emotion, sense of smell, memory, eating, aggression — a whole range of behaviors. It's like an orchestra conductor instead of just an individual musician with specific task."
The temporal area is critical to language and memory, says Keith Black, chairman of neurosurgery at Cedars-Sinai Medical Center in Los Angeles.
"This study raises a lot of questions," says Black, who was not involved in the study. "Will cellphones impact how we remember things, is there any relation to the risk of Alzheimer's? Will it affect our cognitive ability to manipulate language functions?"
Doraiswamy adds, "What would happen if you expose someone's head to a cellphone for three hours a day for six months or against other areas of the head?"
Black says he's concerned about children's increased use of cellphones, since their less developed skulls and brains are more susceptible to the radiation. And he worries about the impact of cellphone radiation over 10, 15, 20 years?
"The important thing to remember about a cellphone is that it's really a microwave radiation antennae. The amount of radiation you get from it is directly related to distance it is from the head," says Black, who recommends plugging in a headset, and says texting is probably OK, too.
On the flip side, "An increase in glucose metabolism doesn't mean it's dangerous," notes Doraiswamy. "Though cancer cells do have higher levels of glucose metabolism, it has also been associated in normal people (and in some animal studies) with some good things, including greater cognitive performance and greater blood flow."
Even so, Doraiswamy says he never uses his mobile phone close to his head. "I always put it on speaker phone."