Do cell phones cause cancer?

We'd all like to know, but unfortunately there's no clear answer — yet. Now an intriguing new study takes a first step toward a possible answer, suggesting that holding your cell phone to your ear does have a measurable effect on the brain, even during cell-phone sessions of less than an hour.

Dr. Nora Volkow, director of the National Institute on Drug Abuse (part of the National Institutes of Health), reports Tuesday in the Journal of the American Medical Association (JAMA) that a cell phone's electromagnetic field can cause changes in brain activity. Specifically, she and her team found that the regions nearest to the antenna of closely held mobile devices showed higher rates of energy (or glucose) consumption.

Before you start to panic that all your cell-phone confessionals have set you up for some kind of brain tumor, remember this: higher rates of glucose metabolism in the brain can mean a number of things. Yes, tumor cells may gobble up more glucose to fuel their relentless growth, but healthy brain cells need constant replenishment too, to keep up the intricate network of messages and connections that help us think, eat, move and stay alive. For now, Volkow isn't ready to say that cell phones' electromagnetic fields can damage the brain, but her findings are the first step toward establishing some much-needed scientific facts about an issue with serious and widespread health implications. Volkow's interest in the topic emerged from both her professional and personal experience. As a brain researcher, her lab has been investigating how energy fields from diagnostic magnetic resonance imaging (MRI) devices can affect brain activity, above and beyond the activity changes they are designed to detect. Imaging tests like MRI are the cornerstone of preventive medicine, helping to detect tumors and other abnormalities early enough to prevent serious and potentially deadly diseases like cancer. But Volkow wondered, How much does the test's magnetic energy itself change the body, however slightly, and do those changes confound the test's results? By studying this question, she discovered that during brain scans, regions of the brain closest to the source of magnetic energy showed higher levels of glucose activity. “That led me to be aware that magnetic fields are sufficiently strong to produce changes in brain glucose metabolism,” Volkow says. Those findingings dovetailed with a more personal observation: Volkow noticed that her sister and spouse tended to spend hours on their cell phones. Knowing the effect that an MRI field had on the brain, she began wondering about the smaller fields emitted by mobile devices. There wasn't much literature on the subject, however, and the few studies that had been done involved only a small number of subjects. So Volkow's group devised a clever trial to test whether the energy from cell phones could cause changes in brain activity. They recruited 47 volunteers who agreed to have their brains scanned with positron emission tomography, a technique that picks up hot spots where cells are consuming glucose. The volunteers held a cell phone to each ear simultaneously, and had their brains scanned twice — once when both phones were off for 50 minutes, and once when only the phone at the right ear was turned on, but muted, for 50 minutes. When turned on, the right-hand phone played a recorded message that the subject couldn't hear in order not to bias the results. Researchers found that the brain regions closest to the active phone's antenna showed the highest rates of glucose activity, and Volkow says the next step is to understand what that means. “Is this a temporary change that recovers every single time, or do chronic, long periods of exposure potentially have long-lasting effects? We need to know that,” she says. The study is the first to look at glucose metabolism as a marker for the effect of a magnetic field. Previous studies have tracked changes in blood flow in the brain, but, as Volkow points, out, blood flow is dependent on cell activity, so glucose use more closely measures how neurons may be affected by phone signals. Because nerve cells make up the majority of the brain, Volkow and her team assume that the heightened activity reflects more excited nerve cells, but she acknowledges that other factors could be at work as well. For example, there may also be more activity in glial cells, which aren't neurons but are critical to feeding energy to nerve cells. Glial cells act on blood vessels to increase the flow of glucose, oxygen and other nutrients that neurons need to send electrical signals throughout the brain. Glia are also important in helping nerves make new connections, and without them, neurons start to die.

The new findings are yet more intriguing data on how cell-phone use may be affecting our health, and while the research is still frustratingly preliminary — it documents changes, but not whether those changes are good or bad — Volkow, for one, isn't taking any chances.

“When you have data like this, you cannot ignore it,” she says. “We need to be guided by objective data. There is data showing that the human brain is sensitive to electromagnetic waves, whether we like it or not. Now we have to understand whether that is bad or good.”

She's purchased a $5 ear piece so she doesn't have to hold her phone to her ear to have a conversation. “I want to play it safe,” she says “What do I lose? Maybe at the end of the day cell phones aren't damaging, but it's only $5.”