October 21, 2011
Danish Study Shows No Link Between Cell Phones And Tumors
A new study from the Institute of Cancer Epidemiology in Copenhagen claims that there is no link between the long-term use of mobile phones and brain cancer, despite previous reports that have made such associations.
With more than 5 billion mobile phone subscribers around the world, fear has grown in many people that the electromagnetic fields emitted by holding a handset to the ear may cause adverse health effects, such as cancerous brain tumors.
The researchers looked at people aged 30 and older who subscribed to mobile phone plans and compared their rates of brain tumors with non-subscribers between 1990 and 2007.
The team found that subscribers of mobile phone contracts of 13 years or more had the same cancer risk as non-subscribers.
“In general, our findings are in line with most of the epidemiological research that has been conducted to date,” Patrizia Frei of the Danish Cancer Society's Institute of Cancer Epidemiology, lead author of the study, told ABC News. “They are also in line with in vitro and in vivo studies that show no carcinogenic effects on the cellular level.”
The findings are in sharp contrast to those from a World Health Organization (WHO) panel of experts. The WHO´s International Agency for Research on Cancer panel concluded in May that cell phones were a possible cause of cancer, which fueled consumers´ fears.
But just over a month later the International Commission on Non-Ionizing Radiation Protection's committee on epidemiology said the scientific evidence increasingly pointed away from a link between mobile phone use and brain tumors.
In June, ABC News asked 92 physicians about their own cell phone use. Sixty-five said they hold their cell phones up to their ear, and 27 said they use hands-free devices to minimize their cancer risk.
A 2010 study found a slight, statistically insignificant increase in risk of a rare form of brain cancer called glioma among cell phone users.
But Timothy Jorgensen, associate professor at Georgetown Lombardi Comprehensive Cancer Center, said: “Most of data that shows an association between cell phones and brain cancer is very weak.”
Such studies are limited by recall bias. People with cancer, desperate for answers, tend to over-report certain behaviors like cell phone use.
Frei and colleagues avoided recall bias by using Denmark´s central population register, a giant database containing health records as well as cell phone plan details for every resident from birth to death. The register also allowed scientists to control for education and socioeconomic factors.
Overall, the researchers found 10,729 central nervous system tumors that occurred in the study period between 1990 and 2007. They say they observed no overall increased risk for tumors of the central nervous system or for all cancers combined in mobile phone users.
“The extended follow-up allowed us to investigate effects in people who had used mobile phones for 10 years or more, and this long-term use was not associated with higher risks of cancer,” Frei and colleagues concluded.
“However, as a small to moderate increase in risk for subgroups of heavy users or after even longer induction periods than 10-15 years cannot be ruled out, further studies with large study populations, where the potential for misclassification of exposure and selection bias is minimized, are warranted,” the team added.
In an accompanying editorial, Professors Anders Ahlbom and Maria Feychting at the Karolinska Institutet in Sweden say this new evidence is reassuring, but has limitations. Cell phone subscriptions were taken as cell phone use. “Having a mobile phone subscription is not equivalent to using a mobile phone,” Ahlbom and Feychting wrote.
“In all of these studies, you have to get information from somewhere,” said Jorgensen. “They assumed that people who subscribe to cell phone plans are using their phones, and I think that's a reasonable assumption. The alternative is to talk to people and ask them to tell you about their cell phone use. But people are notoriously inaccurate.”
Even Frei admits there were limitations in the study.
“We didn´t have any information on the amount of use, so we couldn´t do any sub-analysis on people with heavy phone use,” she said. “There are still some open questions, about greater amounts of use, and about the effects on children.”
Still, the findings should offer some comfort to mobile phone users.
“This paper supports most other reports which do not find any detrimental effects of phone use under normal exposures,” Malcolm Sperrin, director of Medical Physics at Britain's Royal Berkshire Hospital and Fellow of the Institute of Physics and Engineering in Medicine, told Reuters.
On the Net:
- Institute of Cancer Epidemiology, Copenhagen
- British Medical Journal
- WHO International Agency for Research on Cancer
- International Commission on Non-Ionizing Radiation Protection
- Georgetown Lombardi Comprehensive Cancer Center
- Karolinska Institutet
- Royal Berkshire Hospital
- Institute of Physics and Engineering in Medicine