Whether it's something to be concerned about or not remains to be seen. "We don't know that this is harmful," researcher Nora Volkow, MD, director of the National Institutes of Health's National Institute on Drug Abuse, tells WebMD.
In her study, she found those who used a cell phone for 50 minutes had about a 7% rise in glucose metabolism in the brain region closest to the antenna, as documented on PET (positron emission tomography) scans.
So far, Volkow says, her new research shows that "the human brain is sensitive to the electromagnetic radiation that is delivered by cell phones." Beyond that, more research is needed, she says.
The study is published in the Journal of the American Medical Association.
Measuring Brain Metabolism
Volkow and colleagues placed cell phones on the left and right ears of 47 healthy volunteers and then performed the PET scans. They measured the metabolism of glucose in the brain twice, once with the right cell phone activated but the sound muted for 50 minutes (the ''on'' condition) and once with both cell phones deactivated (the "off" condition).
When they looked at overall brain metabolism and compared PET scans, they did not find a difference between the "on" and "off'' conditions. But they did find regional effects -- the 7% boost in the area closest to the antenna when the phone was on.
That area includes the orbitofrontal cortex and temporal pole, involved with such functions as memory and other cognitive skills.
That amount of increase in glucose metabolism, Volkow says, is within the range of increase seen when someone does a cognitive task, such as moving their finger. "It's not a dramatic effect," she tells WebMD. Yet the differences are clear, she says.
The study is believed to be the first to look at brain metabolism in response to cell phone exposure. The next question, Volkow says, is whether there are long-term effects.
Cell Phones and Brain: More Questions
''It's a very interesting finding, the implication of which is unclear," agrees Keith Black, MD, chair and professor of neurosurgery at Cedars-Sinai Medical Center in Los Angeles, who also directs its Maxine Dunitz Neurosurgical Institute and holds the Ruth and Lawrence Harvey Chair in Neuroscience.
He reviewed the findings for WebMD but was not involved in the study.
"Whether [the increased metabolism] could have a long-term effect on memory, on language, is unclear, but it certainly raises those areas as something we need to try to understand," Black says.
The new findings, raising possible concern about the effect of cell phone use on cognitive skills, are not the only unanswered questions about cell phone use, in Black's opinion. "There's been a lot of discussion over the past 10 years about the risk of cell phones and brain cancer," Black says. Whether there is a link or not is not yet fully answered, he says.
Another expert, Paul Thompson, PhD, professor of neurology and a neuroimaging expert at the University of California, Los Angeles, calls the finding ''startling" but also cautions that the implications are not yet clear.
"The unique thing about their study is, they looked at how active brain cells are rather than blood flow," he says. "Blood flow is a reasonable measure of brain function, but it's better to look at the brain cells."
In an editorial accompanying the study, Henry Lai, PhD, of the University of Washington and Lennart Hardell, MD, PhD, of University Hospital in Orebro, Sweden, point out that the study involved participants receiving a muted call from a recorded text and that cell phones in that receiving mode emit less energy than when a user is speaking into the phone.
They write that "the effect observed could thus potentially be more pronounced in normal-use situations."
Cell Phone Industry Perspective
In a statement, John Walls, vice president of public affairs for CTIA -- the Wireless Association, says cell phones are safe.
"The peer-reviewed scientific evidence has overwhelmingly indicated that wireless devices, within the limits established by the FCC [Federal Communications Commission], do not pose a public health risk or cause any adverse health effects," according to Walls.
Volkow suggests using the cell's speaker phone or using an earpiece to keep the antenna away from your head. ''All of the people using a cell phone, like me, are not going to stop using it," Volkow tells WebMD.
Black makes the same recommendations and says he worries especially about children using cell phones. "Their skulls are thinner," he says. "Children are getting a lot more energy from cell phones delivered to their brains than adults."