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: Long-Term mobile-phone use increases risk of benign tumours!” “Clean bill of health for the mobile!” “Mobile phone-cancer link not proven!” Those who have followed the saga of whether or not mobile phones are damaging people’s brains are used to contradictory headlines. A decade of coverage has left readers and viewers more confused than enlightened, with news reports alternating between alarming claims and soothing reassurances. Yet even by the standards of modern news, it is unusual to see such contradictory headlines about the same piece of research. Which is why a study, called Interphone, provides a cautionary tale.
Interphone began in 2000, ended in 2006, cost $30 million and involved around 50 scientists working in 13 countries on 14,000 people. It has, however, still to come to a settled conclusion. A draft of its supposed findings was circulated in June, and Elisabeth Cardis of the Centre for Research in Environmental Epidemiology in Barcelona, who led it, thought until recently that a final paper would be submitted this month. Now, though, it looks as if that will not even happen this year.
The contradictory headlines are the result of national research teams releasing single-country reports, despite the fact that these inevitably involve smaller samples. The results from nine of the 13 single-country studies have been made available in this way, and the consequence is a farrago of misinformation. Many of the national reports suggest, for example, that ever having been a regular mobile-phone user offers statistically significant protection against some brain tumours. This finding is so counter-intuitive that it has led most of the people involved to acknowledge serious flaws in the study’s design.
One problem was what statisticians call selection bias. Interphone began by gathering a group of people who had had the cancers of interest (glioma, meningioma, acoustic neurinoma and parotid gland tumour) and questioning them about their past use of mobile phones. The researchers then approached a number of healthy people in order to compare them with the cancer patients, and find out if there was a systematic difference in mobile-phone use between the two groups. Some of those approached agreed, and some declined. Of those who agreed to take part, 59% were regular mobile-phone users as defined by the study’s protocol. Later on, those who had declined were recontacted and asked about their mobile use. Among this group, only 34% were regular users. That meant those in the control group were...
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