Using a cellphone while driving can be a distracting hazard, but it turns out that simply pressing a cellphone to your ear can cause temporary changes in the brain, according to new research published today by the Journal of the American Medical Association.
The study suggests that cellphones have a subtle effect on brain cells, but does not shed further light on whether cellphones increase the risk of brain cancer, a subject of fierce debate among researchers. Nor does it link cellphone use to any other brain abnormality.
What it does show, however, is that cellphones lead to a temporary increase in brain cells' metabolism of sugar, or glucose, in whatever part of the brain that's closest to the cellphone antenna. The research is the first of its kind to look at that particular area of brain function with regard to cellphone use.
"It's not a dramatic increase," says study author Dr. Nora Volkow, director of the National Institute for Drug Abuse. "It's more in the range of the brain activation that occurs in, say, the language center when you're speaking."
The study was conducted on 47 healthy volunteers who agreed to undergo brain scanning with Positron Emission Tomography -- an imaging test that measures cells' uptake of glucose -- while a cellphone connected to a muted call was attached to their right ear for 50 minutes. The PET scan showed about a 7 percent increase in glucose metabolism in brain regions nearest to the cell phone antenna.
"I wish my study could enlighten brain cancer risks," adds Volkow. "But we donít know whether activation from cell phones could be negative, or even whether it could be beneficial."
Some 91 percent of Americans use cellphones, averaging 21 minutes a day with a phone -- or Bluetooth device -- pressed to their ears. The electromagnetic radiation emitted by such devices appears to activate brain cells and increase their metabolism.
"Even though the health consequences of these effects on brain glucose metabolism are unknown, the results point to a conclusion that cell phone use can possibly affect brain function," write the authors of an editorial that accompanied the study. "The
results warrant further investigation."
Previous population studies of cellphone use and brain cancer risk have come to contradictory conclusions. The latest research published last year in the International Journal of Epidemiology found that overall, cellphone users have no heightened risk for two of the most common types of brain tumors, glioma and meningioma. But a small group of study participants who spent the most total time on cell phones did have some increased risk of glioma.
The latest finding is enough to warn Volkow off of holding her own cell phone directly to her ear. Since seeing the study results, she says she's only using her cell on speaker or with wired ear pieces to keep the antenna away from close contact with her brain.
Bluetooth devices also emit electromagnetic radiation as do cordless phones found in many homes.
"Iím conservative when it comes to my brain. I figure why not play it safe?" she says. Children, she adds, should be particularly careful about cell phone use since their brains are still developing. "I'm more willing to make a recommendation to encourage kids and teens to use the speaker or an ear piece."
Other experts, though, aren't convinced that there's enough evidence to warrant changing cellphone habits.
"This finding is of unknown clinical importance and isn't going to change what I do," says Dr. Dimitrios Trichopoulos, a professor of cancer prevention and epidemiology at Harvard School of Public Health. "Overall, in terms of health effects, I donít think thereís cause for concern."
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