The interpretation of cancer registry data is fraught with problems-- other historical events may impact brain tumor incidence over time (e.g., decreased exposure to ionizing radiation from nuclear weapons testing; increased incidence of allergies; increased use of x-rays and CT brain scans). Other factors that undermine interpretation of tumor incidence trends include the long latency for solid tumor expression (often decades), lags in tumor diagnosis and reporting, under-reporting of tumors, as well as changes over time in diagnostic and screening procedures.
Study eases brain cancer fear, despite increase in cellphone use
Despite increase in cellphone use researchers find ‘no consistent link’ to risk of tumours
Martin Johnston, New Zealand Herald, Feb 26, 2015
New Zealand researchers have found "no consistent increase" in brain cancer during a period of rapidly increasing cellphone use.
They made the same finding, across their 1995-2010 study period, for the particular kinds of tumours that might arise in certain areas of the brain if cellphone use actually did cause cancer.
For all brain cancer counted together, the rate per capita declined by 0.86 per cent a year for people aged 10 to 69. When broken down by sex, age group and type and location of cancer, some groups experienced an increase, but those findings do not implicate cellphones as a cause of cancer.
The University of Auckland findings may come as a relief to frequent cellphone talkers who are anxious they are increasing their risk of a brain tumour, but the study is just one more piece of evidence on the question, which remains not fully answered.
The closest thing to a definitive answer was the 2011 report of the International Agency for Research on Cancer (IARC), which concluded that cellphones and cordless landlines were "possibly" a cause of cancer.
"I don't think [our study] changes the position as described by IARC; it just adds another little piece of the jigsaw," said Professor Mark Elwood, one of the authors of the new study, published today in the Australian and New Zealand Journal of Public Health.
Figures on how many people talk on cellphones and for how long is hard to come by. Instead, Professor Elwood and his colleagues cite telco data to show that cellphone subscriptions increased from 0.2 per cent of the population in 1986, to there being more subscriptions than people by 2007.
There were 4212 cases of cancer of the brain or a related area in the 15-year study period.
The researchers say that if there was a substantial, causal relationship between cellphones and brain cancer, there should be a rise in the incidence of the tumour called glioma in both sexes. And the increase should be greater in the areas of the brain called the temporal and parietal lobes as they are exposed to more radio-frequency radiation than other areas when a person makes voice calls from a phone held to the ear.
They didn't find evidence of either.
The only clear glioma increases were in women aged 30-49, where it was not matched in men of the same age; and in men over 70, where the rise was smaller in the most-exposed areas of the brain.
Professor Elwood said, "Our study adds to the evidence against there being a substantial increase in risk within a short or moderate time-frame.
"That does not exclude the possibility that mobile phones could have a small increased risk or an increased risk with a very long time delay."
Brain cancer study
- 4212 cases of cancer of brain or related areas from 1995 to 2010.
- Rate of brain cancers per capita in people aged 10-69 reduced by 0.86% a year.
- If cellphones caused brain cancer, the rate of glioma cancers in the parts of the brain most exposed to cellphone radiation should have risen (It may have dropped by 0.39% a year).
- Conclusion: Cellphones don't increase brain cancer risk substantially in the short/medium term.
Mr Thorne, 62, sells commercial properties and is based in Takapuna on Auckland's North Shore. Like many real estate agents he does a great deal of work on a cellphone. He has had one since 1990.
He estimates he talks on his cellphone for 600 to 1000 minutes a month. That's about 20 to 30 minutes a day. Ninety-five per cent of his calls are for work.
Mr Thorne said he did not worry about the stories reporting a possible link between cellphone use and brain cancers.
"I have seen lots of speculation about it. We get radio waves from so many sources."
He said that because cellphones had been in use for more than two decades, he believed if they did cause brain cancers then by now there would be clear and certain evidence of this.
"I'm comfortable at this stage."
A father and grandfather of cellphone users, he said, "We've spoken about it. I think you tend to tell your children to do as I say, not as I do.
"I don't have any concerns at this stage. I do need to say 'at this stage' because - who knows?"
--Kim, S. J.-H., Ioannides, S. J. and Elwood, J. M. (2015), Trends in incidence of primary brain cancer in New Zealand, 1995 to 2010. Australian and New Zealand Journal of Public Health. doi: 10.1111/1753-6405.12338
Many ecological studies have been undertaken in various countries to evaluate associations between the use of mobile phones and the incidence of primary brain cancer. The majority of previous studies have relied on data on mobile phone subscriptions to estimate the prevalence of mobile phone use and used cancer incidence data from large population-based cancer registries. The results of many previous ecological studies are summarised in the IARC report,2 which concluded that the overall results of different time-trend analyses do not support the hypothesis that the increase in the use of mobile phones elevates the risk of primary brain cancer. Discussed within that report, Scandinavian4–7 and American studies8,9 found no evidence of an increase in incidence in primary brain cancers from the 1970s to the 2000s, in keeping with the growing number of people using mobile phones over this time period. An exception to this was the 20 to 29 year age group of women in the Inskip et al. study,8 which showed a steady increasing trend in primary brain cancer incidence; however this was due to an increase in frontal lobe cancer, which is an anatomical site not thought to be highly exposed to radiation from mobile phone usage. A UK study found no increase in overall primary brain cancer trends between 1998 and 2007, but did find an increasing trend in temporal lobe tumour incidence in both men and women over the study period.10 In Osaka, Japan, rates at ages 20–74 increased from 1975 to 1988, and at ages 75+ increased until 1984, but then stabilised; these changes were attributed to diagnostic improvements.11 A recent study in Australia based on clinical data showed some increases.12,13 No increases were seen from 1986 to 1998 in a previous study in New Zealand (NZ).14 The present study was undertaken to assess if there had been any increase in more recent years in NZ.
There are no clear causal factors that explain the overall downward trend seen here in the incidence of primary brain cancer in NZ. A decline seems unlikely to be due to late reporting or under-ascertainment, as cancer registration has generally improved over time. Classification issues between benign and malignant tumours may be possible: the NZ Cancer registry does not register benign tumours, so if some types previously regarded as malignant were more likely to be classified as benign, that would lead to a decrease in the recorded incidence of malignant tumours; however, we have no direct evidence of this.
The interpretation of time trends is limited by the lack of information on the latency period for non-ionising radiation exposure from mobile phones (if there is a causal relationship), the limited information on other risk factors, and documentation of the effects of improvements in diagnostic technologies and practices. However, it seems reasonable to conclude that mobile phone exposure has been high in NZ since about 2000, so if this caused a substantial increased risk of brain tumours with a latency of 10 years of less, an increase in incidence would be seen; in fact, at ages 10–69, there have been decreases in the incidence of these cancers.
This study shows no consistent increase in primary brain cancers over the period 1995 to 2010 in NZ and no consistent increasing trends in the incidence of gliomas occurring in temporal or parietal lobe of the brain were seen. This is despite high mobile phone prevalence since 2000 and so does not support the hypothesis that mobile phone usage increases the incidence of brain cancer in NZ, although it cannot exclude a small effect or a latency period greater than 10 years.
Joel M. Moskowitz, Ph.D., Director
Center for Family and Community Health
School of Public Health
University of California, Berkeley
Electromagnetic Radiation Safety
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