Updated May 10, 2016 at 12:10 (see at the end of post)
Recent epidemiological study from Australia, on cell phones and brain cancer, made headline news: Chapman S, Azizi L, Luo Q, Sitas F. Has the incidence of brain cancer risen in Australia since the introduction of mobile phones 29 years ago? Cancer Epidemiology, 2016 May 4.
Reason for this global interest is simple, the authors claim to have proven that cell phones do not cause brain cancer and the issue should be put to rest. The study analyzed the 29 year history of cell phone use in Australia and compared it with the numbers of brain cancer reported to cancer registry.
However, I think the authors greatly overstated significance of their results leading to misinformation of the readers and the general public at large.
The title of the study is correct but it is also misleading. The 29 years since introduction of cell phones in Australia is a correct time-frame. However, the broad introduction of cell phones in Australia begun only after year 2000, after the saturation of the “market” reached 70 – 90% of the population, as shown in Figure 1 of the study.
The other problem is the latency period for brain cancer that Chapman and colleagues used for calculations – only 10 years (!). For brain cancer, a disease that we do not know how it is caused, we do not know what is the time-point when it begins and we do not know what is the period of time before it becomes symptomatic and can be diagnosed, it is not correct to use in calculations only 10-year latency period. It might be so short but, as well, it might be much longer. This is why predictive calculations made by Chapman et al for brain cancer trends with 10 years latency, should be extended to latencies of 20, 30, 40 or even 50 years. Also, the latency might be different for different causes of brain cancer.
In my opinion there are two major problems in this study. First, the misleading claim of 29 years of cell phone use in Australia should be replaced with at the most 15 years, when the phones become really common. Second, use of latency period of 10 years only gives false impression that we should expect that something should be already seen in cancer statistics. If we do not see rise then there is not problem. This is misleading too.
I asked Professor Simon Chapman, Professor Emeritus from the School of Public Health of the University of Sydney, about the two above issues and he, graciously, provided brief answers. With his permission, the questions and answers are copy/pasted below:
Leszczynski: You selected 10 years as the only lag period used in your calculations (page 3 of your manuscript)). How the curves would look like for 20, 30 40 or even 50 years of lag period. Since we do not exactly know what is really the lag period for the brain cancer, it would be more informative to consider several of the possibilities and not only a single, very short (10 years) lag period.
Chapman: We selected a 10 year lag for the reason explained in the paper. I won’t speculate about what the data would look like in 40 or 50 years, but we know that peak incidence of cancers do not appear suddenly out of nothing. The peak is preceded by a steady rise which can be slow at first and then increase. With brain cancer in Australia we are seeing no evidence of any steady rise, so it would be very surprising if suddenly there was any significant and sustained rise.
Leszczynski: Your claim of the 29 year period of usage of cell phones in Australia is correct but at the same time it is misleading. As it comes out from your figure 1, the 70% of saturation with cell phone accounts in Australia was reached only in year 2003. At that time, as I recall myself, the usage of cell phones was limited by the costs. Even though people owned cell phone they limited its usage. Therefore, the really avid use of cell phones, and exposing brains, began only after year 2003. This means that your Australian data should be referred as to analyzing only the last 10-13 years of use, and not 29 years. The first 16 years (from 1987) was the time of a very limited spread of cell phones and of a limited use because of prohibitively high costs, at least for private users.
Chapman: I’m afraid I don’t agree at all that “avid use” of mobile phones began only after 2003 in Australia. Figure 1 sourced from both the Australian government regulator & the mobile communication industry show that 70% of Australians were using mobiles by 2003, with about 1 in 4 using them by 1997.
From the answers of Professor Chapman, clearly appears that our opinions differ and that he does not accept my concerns. Likewise, I do not accept Professor Chapman’s explanations.
Also, the authors of the study did not provide any information on where from the funding was provided. It is important omission. The journal of Cancer Epidemiology should have asked and insisted on providing this. Transparency in the area on the border of business and science is important.
In my opinion the authors of the study overstated their findings and misled the non-scientific readers. No study is perfect and every study can be improved. However, providing unfounded conclusions, not supported by the evidence is wrong.
The conclusion of the Australian study: “…After nearly 30 years of mobile phone use in Australia among the millions of people, there is no evidence of any rise in any age group that could be plausibly attributed to mobile phones…” is completely false because it is not supported by the evidence.
Update: read also comment, submitted by Prof. Chapman in response to my blog post, available below.