Cellphone use appears to increase brain activity in regions close to where the phone antenna is held against the head, according to a new study, but researchers said the health implications are still unknown.
The study is the first to demonstrate that radiation from the devices has a direct impact on some brain cells, and is likely to fuel a long-running debate over the safety of cellular phones.
"This study shows that the human brain is sensitive to electromagnetic radiation coming out of cellphones," said Nora Volkow, an author on the study and a scientist at the National Institutes of Health. "That is something we need to face."
Shirley Wang has details of a just-released study indicating that cell phone use does have a direct impact on brain activity.
However, "our finding does not tell us if this is harmful or not," said Dr. Volkow, who is also the head of the National Institute on Drug Abuse.
Some medical experts have been concerned for years about the possible long-term health consequences of frequent cellphone use. The city of San Francisco voted in June to require cellphone retailers to post the amount of radiation emitted by each phone because of the concern.
But results from studies looking at the health effects have been mixed. Some large-scale studies have found a link between cellphone use and brain cancer, but they haven't been able to show the cancer was caused by cellphone radiation.
The main concern is that radiation from phones could cause DNA mutations or changes in the brain, leading to tumors or cognitive decline. But to date there is no known evidence that the frequency of the waves emitted from phones is powerful enough to cause such changes, according to Reto Huber, a professor at the University Children's Hospital Zurich who has published several studies on electromagnetic fields and cellphones. He wasn't involved in this latest study.
In Tuesday's study, published in the Journal of the American Medical Association, researchers from the National Institutes of Health and Brookhaven National Laboratory in New York examined the impact of cellphone use on brain activity by measuring the glucose metabolism—how much sugar a cell takes in to fuel activity—of 47 adults, the largest study of its kind to date. They conducted scans while subjects had cellphones held to their left and right sides for 50 minutes. The researchers found that some brain regions near the antenna became significantly more active when a cellphone was turned on and held to the ear, even though the participants didn't actually speak or listen to a conversation.
The increase in brain activity in those regions was comparable to the increase in level of glucose metabolism used by the visual cortex when someone talks—about 8% to 10%, according to Dr. Volkow.
Dr. Huber's group in Switzerland has conducted similar studies by measuring blood flow to brain regions—another indicator of brain activity—and found that there is an increase in flow to regions close to where the cellphone was held.
Mitchel Berger, a neuro-oncologist at the University of California, San Francisco, called the findings "very interesting and provocative" but said they don't increase his concerns about the safety of cellphones.
"You could get confused very rapidly and think this finding is equated with a health hazard," said Dr. Berger, who wasn't part of the study. "What it tells us is at the frequencies these phones currently generate, there are [brain] regions that are hyperactive."
Nevertheless, "I think until we really understand the very long-term effects with these newer phones it's not unreasonable to ask people to use headphones or speakers," said Dr. Berger.
If there aren't negative long-term effects, cellphones could be used as a non-invasive way to stimulate parts of the brain in a therapeutic sense, such as for depression treatment, said Dr. Volkow.
http://online.wsj.com/article/SB10001424052748704071304576160652541652440.html
posted by In Kyong Lee
