In a four-country study published this week in the Journal of the National Cancer Institute, researchers matched 352 children and adolescents diagnosed with brain cancer with 646 similar kids who were healthy, and compared their patterns of cellphone use. The children ranged in age from 7 to 19, and researchers asked how long they had been regular users of mobile phones, which ear they tended to favor, and whether they ever used a hands-free device.
In the overall sample, children whose cellphone use had started earlier and continued for the longest time were not more likely to develop brain cancer. But in the small group of children for whom the researchers had cellphone-company records of a child's earliest use, researchers did find a statistically significant increase in brain cancer risk for those who had their first cellphone earliest. While that may raise a flag, it's not clearly red: Among kids who took up the habit earlier, a higher number of calls made on a child's phone, or a larger accumulation of time spent on the phone, didn't predict higher brain cancer rates.
"The available evidence does not support a causal association between the use of mobile phone and brain tumors," the authors reported.
The findings of the study, conducted in Sweden, Norway, Denmark and Switzerland, are in line with those of a number of comprehensive studies completed, both in failing to find a strong causal link and in turning up a few worrisome exceptions. The Interphone Study, a 10-year, $14-million study that spanned 13 countries and released its findings in May 2010, failed to find a significant link between cellphone use and cancers of the brain, parotid gland or acoustic nerve. But it did find weak evidence that the heaviest cellphone users might be at increased risk for glioma — one type of brain cancer — and declared that further study was in order.
Kids' increased vulnerability to harm from cellphone use, especially, has been widely hypothesized. Their smaller heads mean that heat and electromagnetic waves could penetrate more deeply into their brains. And, of course, they will, over their lifetimes, probably rack up much larger cellphone exposures than any adult now living, because their use of cellphones has started early and their reliance on the technology will be more extensive.
These findings may be unsurprising to scientists who continue to assert that electromagnetic waves cannot be a cause of cancer because their energy is too weak to cause DNA damage or disrupt cell function, the catalyst for cancer formation. But some researchers and activists continue to believe there is a link. A more recent study has found that brain activity changes with cellphone use, suggesting that the full effects of cellphones have yet to be uncovered. So more research is in the offing.