Bias in mobile phone study affected cancer link – expert
The largest international study carried out to date into mobile phones and brain cancer found no conclusive evidence of a link between the two.
The University of Sydney’s lead Australian author of the Interphone study Professor Bruce Armstrong said some bias within the study meant a definitive link could not be proven.
“My take on the Interphone study is that yes we do have some suggestions of an increased risk but we cannot confidently say there is or isn’t a risk on the basis of these suggestions,” he said this week.
The Interphone International study, which began 10 years ago and involved 10,000 people from 13 countries, selected and interviewed mobile phone users who had been diagnosed with a brain tumour, as well as healthy individuals.
Each was asked to recall their mobile phone use from when they began using a mobile phone to the present.
One confusing result of the study showed mobile phones were actually protective against brain tumours, meaning mobile phone users had a lower risk of brain cancer than those who had never used one, Professor Armstrong said.
But he added this could be explained by a participation bias.
“Participation in the study was voluntary and we found that those who refused were less likely to be mobile phone users than those who agreed to participate.”
Once you have bias in your data it’s very hard to get rid of its effects and be confident in the results, he said.
Data also showed that the 10 percent of people who used their phones the most had a greater risk of developing a brain tumour, but these results may be the result of recall inaccuracies.
“Those with brain tumours tended to over recall usage in the more distant past which could create a bias,” Professor Armstrong said.
Cancer Council Australia’s scientific advisor, Professor Bernard Stewart, said there were untold tens of millions of people who used mobile phones.
“In light of the huge population who do use mobile phones further research is necessary and that’s what investigators recommended and that’s what’s to be endorsed,” he said.
“But at the moment there is no cause for anxiety amongst people who use mobile phones that they are at risk of brain cancer. We simply have to acknowledge that the research has been well done but it leaves matters which should be further studied and that’s where we should go from here.”
A follow-up study to Interpol is in the planning stage for research into the link between mobile phone usage and brain tumours in adolescents and younger adults.
Monash University Professor Malcolm Sim is heading the Australian arm of this international study, called the Mobi-kids study.
“We hope to start collecting data late this year but will not have results for several years,” he said.
UK scientists last month launched a study into the effects of mobile phones on
long-term health. The Cosmos study will follow 250,000 people in five European countries for more than 20 years. It is considered more accurate than the Interpol study as it tracks people’s usage in real-time.