Long-term study of cellphone use finds no cancer link

Posted by Emma Woollacott

In what's described as the largest ever study on the cancer risk of cellphones, Danish researchers have found no link between phone use and brain tumors.

There is no link between long-term use of mobile phones and tumours of the brain or central nervous system, finds new research published on bmj.com today.

The team surveyed 358,403 mobile phone subscribers over an 18-year period, following up on the subjects of an earlier study.

They studied data on the whole Danish population aged 30 and over and born in Denmark after 1925, divided into subscribers and non-subscribers of mobile phones before 1995. Information was gathered from the Danish phone network operators and from the Danish Cancer Register.

Overall, 10,729 central nervous system tumours occurred in the study period 1990-2007.

When the figures were restricted to people with the longest mobile phone use – 13 years or more – cancer rates were almost the same in both long-term users and non-subscribers.

There was no overall increase in risk for either tumours of the central nervous system or for all cancers combined.

"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," says the Institute of Cancer Epidemiology in Copenhagen team.

"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 minimised, are warranted."

Previous studies on a possible link between phone use and tumors have been inconclusive - partly because, with cellphones a relatively recent phenomenon, there was little data on the effects of long-term use.

However, some studies have indicated a link, leading the International Agency for Research on Cancer (IARC) to recently classify cellphone radiation as possibly carcinogenic to humans.

And the Danish study has already been criticized.

"In order for any study of a relatively rare disease like brain tumors to find a change in risk, millions must be followed for decades.  By extending an earlier analysis on the same group of cellphone users, this new report provides unsurprising, biased and misleading conclusions," says Devra Davis, president of the Environmental Health Trust.

"It uses no direct information on cell phone use, fails to consider recent and rapidly changing nature and exposure to microwave radiation from cellphones, cordless phones and other growing sources, and excludes those who would have been the heaviest users — namely more than 300,000 business people in the 1990s who are known to have used phones four times as much as those in this study."