We have had mobiles in Australia since 1987. Some 90% of the population use them today and many of these have used them for a lot longer than 20 years. But we are seeing no rise in the incidence of brain cancer against the background rate (Simon Chapman, Emeritus Professor in Public Health, University of Sydney).
We examined the association between age and gender-specific incidence rates of 19,858 men and 14,222 women diagnosed with brain cancer in Australia between 1982-2012, and national mobile phone usage data from 1987-2012.
In summary, with extremely high proportions of the population having used mobile phones across some 20-plus years (from about 9% in 1993 to about 90% today), we found that age-adjusted brain cancer incidence rates (in those aged 20-84 years, per 100,000 people) had risen only slightly in males but were stable over 30 years in females.
There were significant increases in brain cancer incidence only in those aged 70 years or more. But the increase in incidence in this age group began from 1982, before the introduction of mobile phones in 1987 and so could not be explained by it. Here, the most likely explanation of the rise in this older age group was improved diagnosis.
Computed tomography (CT), magnetic resonance imaging (MRI) and related techniques, introduced in Australia in the late 1970s, are able to discern brain tumours which could have otherwise remained undiagnosed without this equipment. It has long been recognised that brain tumours mimic several seemingly unrelated symptoms in the elderly including stroke and dementia, and so it is likely that their diagnosis had been previously overlooked.
Next, we also compared the actual incidence of brain cancer over this time with the numbers of new cases of brain cancer that would be expected if the “mobile phones cause brain cancer” hypothesis was true. Here, our testing model assumed a ten-year lag period from mobile phone use commencement to evidence of a rise in brain cancer cases.
Our model assumed that mobile phones would cause a 50% increase in incidence over the background incidence of brain cancer. This was a conservative estimate that we took from a study byLennart Hardell and colleagues (who reported even higher rates from two studies). The expected number of cases in 2012 (had the phone hypothesis been true) was 1,866 cases, while the number recorded was 1,435.
Using a recent paper that had Davis as an author we also modelled a 150% increase in brain cancer incidence among heavy users. We assumed that 19% of the Australian population fell into this category, based on data from the INTERPHONE study an international pooled analysis of studies on the association between mobile phone use and the brain. This would have predicted 2,038 expected cases in 2012, but only 1,435 were recorded.
In Australia, all cancer is notifiable. At diagnosis, all cases must by law be registered with state registries tasked with collecting this information. It has been this way for decades. So we have excellent information about the incidence of all cancers on a national basis.
The telecommunications industry of course also has information on the number of people with mobile phone accounts.
While touring Australia, Davis was confronted with the “flatline” incidence data on brain cancer. Her stock response was that it was far too early to see any rise in these cancers. She was here to warn us about the future.