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Data Caps Brain Cancer Concerns

Cedit: pathdoc/Adobe

Cedit: pathdoc/Adobe

By Mark Elwood & Stella Kim

Extensive health data records in New Zealand have revealed whether brain cancer rates have changed as a result of radiation emitted by mobile phones.

There have long been fears in the community about whether the use of mobile phones could lead to an increase in the frequency of brain tumours. However, our analysis of data collected by The New Zealand Cancer Registry between 1995 and 2010 has found that the risk of developing a brain tumour has not changed significantly despite the increased use of mobile phones during that time.

In fact, for those aged 10–69 years there has been a decrease of about 1% per year. In people aged over 70 years there was an increase in some types of brain cancer, but this has been seen in other countries and is likely to be due to improved diagnosis.

Our study, published in the Australian and New Zealand Journal of Public Health (www.tinyurl.com/ptynwqe), adds to existing evidence against a substantially increased risk in mobile phone users, and is consistent with most similar studies conducted in other countries. However, a study of this type cannot exclude the possibility of a small risk, or a risk limited to a certain subtype of cancers, or a risk that only arises after more than 15 years of phone use.

Put that way, our research results sound pretty simple and straightforward, but reaching those conclusions took a great deal of thought and hard work.

Stella had completed the 3 years of the Bachelor of Health Science program and had chosen to do an Honours year, which requires a research dissertation. She was interested in epidemiology, and Mark suggested she examine whether there been an increase in the incidence of brain cancers in New Zealand in recent years. This is an important question because almost everybody uses a cell phone these days, and the idea that cell phones increase brain cancers because of their electromagnetic radiation is a familiar one.

While the popular concept of science is that the development of such a scientific study involves deep contemplation and challenging original thought, in practice the questions asked when selecting a study are often are very practical. Can we get data? Do we need funding? What do we do about ethical approval?

The mobile phone study was only feasible because New Zealand, like most other developed countries, has a national cancer registry: that is, a system by which every newly diagnosed cancer in the country is reported to a group within the Ministry of Health.

So we asked the cancer registry to give us information on every person with a brain cancer diagnosed and recorded in New Zealand between 1985 and 2010 (the most recent year available) as a simple Excel spreadsheet. This record had their age, gender, date of diagnosis, and details about the cancer such as its pathology (there are several different types of brain cancer) and its location within the brain. The information we did not want, and which the registry would not have given us anyway, was anything that could identify the individual: their name, address, hospital number and so on. This information is, of course, strictly protected to maintain privacy.

But to get the information from the Registry, we had to tell them what we would use it for and get ethical approval from our university. Fortunately this was relatively simple as we were not asking for any identifiable information, and the study did not involve direct contact with patients to review medical records or conduct interviews. Any substantial study involving interviews with patients, travelling to different hospitals, or other expenses requires an application for funding, which is almost always a very slow and uncertain process. It may even take longer than doing the research itself. So the ethical approval process was simple, and we did not require any funding.

The research itself involved getting the data from the cancer registry and analysing it, so Stella had to learn several statistical techniques. She also had to learn a lot about brain cancer, such as the areas of the brain most likely to be affected by radiation from a mobile phone. And she also had to learn about mobile phones, electromagnetic energy and so on.

In addition, Stella had to review the literature on the issue of mobile phones and brain tumours. This is very complex; there are many epidemiological studies of different designs, some strong and some weak, and often with conflicting results. While she didn’t have to review the information in so much detail, she had to understand how the results of animal experiments and cellular and metabolic studies using radio frequency energy contributed to the evidence.

In the end, Stella ran a lot of different analyses. We ended up concentrating on the specific type of cancer that earlier studies had identified as the main source of risk – a cancer not of neurons but of glial cells that support the neurons – and the two regions of the brain that would be most heavily exposed to energy from a cell phone.

Even then we had several age ranges, and of course data for men and women separately. One of the major issues in interpretation is that you may find a trend in one age range and one gender, and not find it in other groups. So although the final paper seems relatively straightforward and has only a few results, Stella’s Honours dissertation includes a lot more results.

While we did not find an association between the use of mobile phones and the incidence of brain cancer, this doesn’t mean that mobile phone usage cannot possibly increase the incidence. In fact, we need to think about what the latency period for the effect of mobile phone usage would need to be for the increase not to show up in our study.

Stella Kim is a research student supervised by Mark Elwood, who is Professor of Cancer Epidemiology at The University of Auckland’s School of Population Health.