Blog | Friday, October 21, 2011

QD: News Every Day--'Zero bars' for connection between cell phones, cancer

There is no link between long-term use of mobile phones and tumors of the brain or central nervous system. In what is described as the largest study on the subject to date, Danish researchers found no evidence that the risk of brain tumors was raised in cell phone users with up to 18 years of use.

Old Motorla Mobile by garryknight via Flickr and a Creative Commons licenseResults appeared Oct. 20 at BMJ.

There were more than five billion service plans in effect worldwide in 2010, the authors wrote in their study. The International Agency for Research on Cancer (IARC) recently classified radio frequency electromagnetic fields as emitted by mobile phones as possibly carcinogenic to humans.

In this latest update, researchers led by the Institute of Cancer Epidemiology in Copenhagen continue their study up to 2007. They studied data on the whole Danish population aged 30 and over and born in Denmark after 1925, subdivided 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.

The researchers say they observed no overall increased risk for tumors of the central nervous system or for all cancers combined in mobile phone users.

Specifically, 358,403 subscription holders accrued 3.8 million person years of cell phone use. There were 10,729 cases of tumors of the central nervous system from 1990 to 2007. The risk of such tumors was the same for men and women.

When restricted to individuals with the longest mobile phone use of more than 13 years, the incidence rate ratio was 1.03 (95% confidence interval [CI], 0.83 to 1.27) in men and 0.91 (95% CI, 0.41 to 2.04) in women. Among those with subscriptions of more than 10 years, ratios were 1.04 (95% CI, 0.85 to 1.26) in men and 1.04 (95% CI, 0.56 to 1.95) in women for glioma and 0.90 (95% CI, 0.57 to 1.42) in men and 0.93 (95% CI, 0.46 to 1.87) in women for meningioma.

There was no indication of dose-response relation either by years since first mobile phone use, or in cases of temporal glioma, where brain cancers might arise due to proximity to where people usually hold their handsets.

The authors wrote, "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."

In an accompanying editorial, reviewers said, "The search for an association between mobile telephone use and cancer risk should be viewed in the context of its origin. It did not originate from a particular biophysical hypothesis or results of a seminal study but from a concern that some aspect of the interaction between radiofrequency fields and human physiology has been overlooked or misunderstood. The research that has been conducted for the safety of public health with regard to this new and rapidly spreading technology is now extensive. The question is how much more research is needed. Continued monitoring of health registers and prospective cohorts is warranted, but more case-control or other studies with built in selection and recall bias are not needed."