"We did not find that young mobile phone users have an increased risk for brain tumors when regularly using mobile phones," says study researcher Martin Roosli, PhD, of the Swiss Tropical and Public Health Institute, University of Basel.
Nor did they find a link with longer use. "We did not see that the risk increased after five years or more since the first use of mobile phones," he tells WebMD.
The study is believed to be the first to research cell phone use among youth with brain tumors.
Roosli calls the results ''reassuring."
However, he adds a caveat: "The amount of use in our study is relatively low," he says.
Regular users in the study, conducted from 2004 to 2008, were defined as those who talked at least once a week for six months or more. "Nowadays, I think young people use [cell phones] more," Roosli says.
Like other experts, he urges continued study and monitoring.
The study is published in the Journal of the National Cancer Institute. Among the funding sources is the Swiss Research Foundation on Mobile Communication. The organization had no input into the research, Roosli tells WebMD, and was not informed of the results before publication.
Cell Phones and Kids
Roosli and his team looked at the medical records of 352 children and teens ages 7 to 19 who had been diagnosed with brain cancers.
In interviews, the researchers asked the youths and their parents about mobile phone use. Phone service providers also provided some information.
The youngsters were from Norway, Denmark, Sweden, and Switzerland.
For comparison, the researchers turned to 646 children and teens matched by country, age, and sex. They asked them for the same information.
Roosli took into account whether the youngsters used hands-free devices or not.
Among the results:
- Regular users of mobile phones were not more likely to be diagnosed with brain cancers. While over 75% of the brain cancer patients had talked on a mobile phone more than 20 times before the diagnosis, 72% of the healthy young people had done so in the same time period.
- Children who began to use cell phones at least five years earlier did not have a higher risk of brain cancer compared to nonusers.
- A small subset of 24 brain cancer patients and 25 healthy youths had data from the phone providers. For these kids, Roosli found cancer risk was related to the amount of time the youth had a phone subscription, but not to the amount of use. This could be due to factors such as brain cancer patients being more diligent about getting information from providers, Roosli tells WebMD.
- The parts of the brain with the highest exposure to the phone's radio-frequency waves were not linked with an increased risk of brain cancer among regular users.
The incidence of brain cancers has not risen over the last 20 years in countries with widespread cell phone use, Roosli says. The further refutes a link, he says.
Even so, he says, cancer registries should continue to monitor trends in cancer rates.
Risk and Reassurance
"It's reassuring," says Robert Tarone, PhD, biostatistics director of the International Epidemiology Institute in Rockville, Md., and professor of medicine at Vanderbilt University in Nashville.
He co-authored an editorial to accompany the study.
He notes that more than 91% of the U.S. population now subscribe to cell phone service. More than 5 billion people do globally.
"If cell phones cause brain cancer, we are going to see it in the rates," he tells WebMD. "We haven't seen it yet."
However, he says, some experts bring up the question of latency -- the time between exposure and a cancer diagnosis.
For that reason, he says, he agrees with the Swiss researchers that the rates of brain cancer in the population should continue to be monitored. However, he says, the kind of ''look-back'' studies done by Roosli are not proving useful.
A better approach, he says, is to monitor phone users over time, going forward.
Tarone points to other recent studies, largely reassuring that cell phones are not linked with cancer risk.
In his editorial, he talks about an agency of the World Health Organization recently announcing that cell phones may be ''possibly carcinogenic." The change, he says, is based on what the agency calls ''limited evidence" of a cancer link. The conclusion, Tarone says, reflects the fact that there is very little scientific evidence about cell phones and cancer. It's not a call to abandon cell phones, he says.
On its web site, the World Health Organization says that an increased risk of brain tumors with cell phone use is not established. However, it says more research is needed.
For parents and others still wary, Tarone says, ''there are ways to use cell phones so you don't get it near your head. It's the antenna that has the energy."
Measures such as speaker phones and hands-free devices reduce the radio-frequency energy exposure.