The first in a series of eagerly anticipated nationwide studies has concluded that the use of mobile phones poses no increased risk of brain cancer – at least not for the first 10 years.
Despite this caveat, the Danish study is likely to carry more weight with health authorities and scientists than many previous studies because of its large sample size and careful design. Earlier studies that claimed to find evidence of a health risk have been criticised for weaknesses in these areas.
The new work is the first to be published from the huge INTERPHONE study, organised by the International Agency for Research on Cancer (IARC). It involves 13 different countries and aims answer definitively the question of whether mobile phone use is safe.
In the short term, the study indicates there is no danger of developing tumours, says principle investigator Helle Christensen, at the Institute of Cancer Epidemiology in Copenhagen. Michael Clark, of the UK’s National Radiological Protection Board, is impressed by the work: “This is an authoritative study.”
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When the data from all 14 studies is collected over the next 18 months, the number of long-term users should be large enough to reveal any small increases in risk beyond 10 years of use, says Elizabeth Cardis of the IARC, who will be carrying out the final INTERPHONE analysis.
Population based
One key aspect of the new study is that it was “population-based”, i.e. the researchers attempted to recruit every new case of a rare brain tumour in Denmark’s entire population of 5.3 million people over a two year period.
In total, 106 people were identified and their phone usage and medical records were then compared with those of 212 randomly chosen controls, matched for age, sex and socio-economic status. The researchers found no difference in mobile phone use between the two groups.
The tumour type studied, called an acoustic neuroma, is a rare benign tumour that forms between the brain and the inner ear. “It’s located right where the radiation is most intense,” Christensen told New Scientist. “If mobile phones are in some way able to influence tumour tissue, it should be able to influence acoustic neuromas.”
Too few of the subjects had used phones for more than 10 years to tell if there was a long-term risk, she says. There were not just fewer people using phones back then, says her colleague Christoffer Johansen, those that had mobiles also used them much less frequently than they do today.
The researchers found no correlation between the side of the head on which the phone was used and the side on which tumours formed. And no difference was seen between people who started using old analogue phones or the more recent digital phones.
Journal reference: American Journal of Epidemiology (vol 159, p 277)
