Dec. 3, 2009 -- Scientists say they could find no substantial change in the incidence trend of brain tumors among a study group of 60,000 people five to 10 years after cell phone usage rose sharply in the countries where they lived.
Cell phones have been mentioned for years as possible causes of brain tumors, but the new study, published in the Dec. 3 online issue of the Journal of the National Cancer Institute, found no cell phone-related increase during this study period.
Researchers from Denmark, Finland, Norway, and Sweden say they found that the incidence of brain tumors in the studied population of people from the four countries remained stable, decreased, or showed only a gradual increase that started before the introduction of the wireless devices between 1974 and 2003.
Mobile phone use in those Nordic countries rose dramatically in the mid-1990s, the study says.
Lead author Isabelle Deltour, PhD, of the Institute of Cancer Epidemiology of the Danish Cancer Society, and colleagues say they found no change in incidence trends of brain tumors in data going back to 1998.
They mentioned several possible reasons for their finding:
- The induction period relating cell phone use to brain tumors exceeds five to 10 years;
- The increased risk is too small to be observed;
- The increased risk is restricted to subgroups of brain tumors or cell phone users;
- There is no increased risk of brain cancer by using cell phones.
The authors say they didn’t examine cell phone usage at the individual level during the time period studied, only the incidence of brain tumors.
“Because of the high prevalence of mobile phone exposure in this population and worldwide, longer follow-up trends in brain tumor incidence are warranted,” the authors write.
The U.S. Food and Drug Administration says on its Web site that “The weight of scientific evidence has not linked cell phones with any health problems.”
The agency continues to monitor findings of new and ongoing studies. The federal agency says that wireless phones emit low levels of radiofrequency energy. This is different than radiation from X-rays.
The American Cancer Society says that in looking at most studies as a whole, no link between cell phones and tumor development has been found.
Deltour and colleagues, who studied data on 59,984 men and women aged 20-79 diagnosed with brain tumors, say that if there is a linkage between the disease and cell phone use, the numbers don’t reveal it.
"Our finding that brain tumor incidence rates were either stable, decreased, or continued a gradual increase that started before the introduction of mobile phones is consistent with mobile phone use having no observable effect on brain tumor incidence…,” the authors conclude.
They add that population groups that are heavy mobile phone users should be studied for longer periods of time.
Michael Thun, MD, vice president emeritus, of the ACS, tells WebMD that “this is a good study” that “clearly shows the incidence” of brain tumors doesn’t increase after a period of five to 10 years.
However, he says more research needs to be done to see if longer-term use can cause tumors.
"That’s important, because it’s an incredibly widely-used technology,” he says. “The study doesn’t answer the question of what happens after 50 years.”
John Walls, a vice president of the mobile industry trade group, CTIA-The Wireless Association, says “peer-reviewed scientific evidence has overwhelmingly indicated that wireless devices do not pose a public health risk” and that the ACS, the NCI, the World Health Organization and the U.S. Food and Drug Administration “all have concurred that wireless devices are not a public health risk.”