Cellphone use tied to brain activity

The researchers, led by Dr Nora D Volkow, director of the National Institute on Drug Abuse, urged caution in interpreting the findings because it is not known whether the changes, which were seen in brain scans, have any meaningful effect on a person’s overall health.

But the study, published on Wednesday in The Journal of the American Medical Association, is among the first and largest to document that the weak radio-frequency signals from cellphones have the potential to alter brain activity. “The study is important because it documents that the human brain is sensitive to the electromagnetic radiation that is emitted by cellphones,” Volkow said. “It also highlights the importance of doing studies to address the question of whether there are—or are not—long-lasting consequences of repeated stimulation, of getting exposed over five, 10 or 15 years.”

Although preliminary, the findings are certain to reignite a debate about the safety of cellphones. A few observational studies have suggested a link between heavy cellphone use and rare brain tumours, but the bulk of the available scientific evidence shows no added risk. Major medical groups have said that cellphones are safe, but some top doctors have urged the use of headsets as a precaution.

Volkow said that the latest research is preliminary and does not address questions about cancer or other heath issues, but it does raise new questions about potential areas of research to better understand the health implications of increased brain activity resulting from cellphone use.

When asked to comment on the latest study, the leading industry trade group, CTIA—The Wireless Association, released a statement emphasising recent studies that have shown no elevated cancer risk associated with cellphone use.

“The peer-reviewed scientific evidence has overwhelmingly indicated that wireless devices, within the limits established by the FCC, do not pose a public health risk or cause any adverse health effects,” said John Walls, vice-president of public affairs for the trade group, adding that leading global health groups “all have concurred that wireless devices are not a public health risk.” But the new research differed from the large observational studies that have been conducted to study cellphone use. In Volkow’s study, the researchers used brain scans to directly measure how the electromagnetic radiation emitted from cellphones affected brain activity..

The randomised study, conducted in 2009, asked 47 participants to undergo positron emission tomography (PET) scans, which measure brain glucose metabolism, a marker of brain activity. Each study subject was fitted with a cellphone on each ear and then underwent two 50-minute scans.

During one scan, the cellphones were turned off, but during the other scan, the phone on the right ear was activated to receive a call from a recorded message, although the sound was turned off to avoid auditory stimulation.

Whether the phone was on or off did not affect the overall metabolism of the brain, but the scans did show a 7 per cent increase in activity in the part of the brain closest to the antenna. The finding was highly statistically significant, the researchers said. They said the activity was unlikely to be associated with heat from the phone because it occurred near the antenna rather than where the phone touched the head.

In the past, any concerns about the health effects of cellphones have been largely dismissed because the radiofrequency waves emitted from the devices are believed to be benign. Cellphones emit nonionising radiation, waves of energy that are too weak to break chemical bonds or to set off the DNA damage known to cause cancers. Scientists have said repeatedly that there is no known biological mechanism to explain how nonionising radiation might lead to cancer or other health problems.