When findings from the largest study of the possible link between cell phone use and brain cancer were released in May, media reports on its conclusions varied widely. "Heavy Mobile Users Risk Cancer," read one headline. "No Proof of Mobile Cancer Risk," proclaimed another. Which, if either, was true? It's no small question, considering that 91% of Americans have cell phones, and the number of users worldwide will reach 5 billion this year.
INTERPHONE, the $24 million study sponsored by the World Health Organization's International Agency for Research on Cancer (and funded in part by the wireless industry), found no overall increase in the risk of glioma or meningioma in average cell phone users and "suggestions of an increased risk of glioma" among the heaviest users—those who averaged about a half hour of use per day over 10 years. The researchers couldn't make "a causal interpretation" of that finding, they wrote, because of study "biases and errors."
Some of those biases can be inherent in a case–control design, one type of observational research. INTERPHONE matched "cases" (roughly 5,000 people from 13 countries with meningioma or glioma diagnosed between 2000 and 2004) with "controls" (about 5,600 demographically comparable people without brain tumors). Researchers interviewed subjects about their cell phone use and then undertook "hundreds of different analyses" in sorting through "methodological issues," said Elisabeth Cardis, INTERPHONE's lead researcher, now at the Centre for Research in Environmental Epidemiology in Barcelona. One issue that likely skewed the findings was recall bias, in which some subjects with cancer exaggerated their cell phone use. Cardis told AJN by e-mail that such issues are typical of this type of study and led to "legitimate differences of opinion among investigators."
Journalists are obligated to describe such flaws, said Gary Schwitzer, publisher of HealthNewsReview.org, which evaluates the quality of health-related news reports. "It is simply inaccurate to use the phrase 'can increase risk' when reporting on results of a study that is incapable of showing a causal link," he said. Doing so can result in what he calls "editorial ping-pong"—with volleys between news outlets claiming "yes, it causes illness" and "no, it doesn't"—which "may lead the public to lose confidence in science and scientists."
Several case–control studies of smokers, published in 1950, provided some of the earliest evidence of the link between smoking and lung cancer. Yet with the inconclusive findings and study flaws seen in INTERPHONE, nurses might find it hard to know whether to recommend precautions to patients, said Carlton G. Brown, president of the Oncology Nursing Society. Until a better-controlled study determines whether the radiation emitted by a cell phone held to the head increases the risk of brain cancer, he advises a precautionary approach. "Maybe we should use headsets," he said.
Many bedside nurses don't seem too concerned about the possible risks of cell phone radiation, said Sandra Ng, informatics nurse specialist and manager at the University of California San Francisco Medical Center, where she specializes in implementing new technologies. All facilities incorporating wireless technologies have to ensure that products they use abide by Federal Communications Commission regulations, she said, and although most nurses in her facility carry a device, "there's not enough definitive evidence showing a link. We should continue to keep an eye on it."
In June, around the time that Apple sold 1.7 million of its new iPhone 4 in just three days, San Francisco became the first city in the country to require retailers to disclose each cell phone's specific absorption rate—also known as SAR, the amount of electromagnetic radiation absorbed through use. Will such information help or hinder the public's understanding of potential health risks? Only time will tell.—Joy Jacobson
Cardis E, et al., for the INTERPHONE Study Group. Int J Epidemiol