HELINSKI, December 16, 2011 (update Dec. 21, 2011) –The science of epidemiology examines what happens when portions of population are exposed to agents that might, or might not, affect the health. The major problem of epidemiological studies is the heterogeneity of human population caused by heredity and by environment.
In spite of the limitations, epidemiological studies are often seen as the most important type of studies and they give the most weight to health-risk decisions.
Recently the Danish Cohort epidemiological study, (British Medical Journal p.2011), is receiving attention in the news media, from decision makers and from the cell phone industry. The conclusion of the study is that there is no causal link between brain cancer and cell phone radiation.
Many have “bought” this claim but many others are questioning it. A number of scientists, including myself, entirely disagree with the conclusions of this study. Critical comments have been written and submitted to the British Medical Journal. (update Dec. 21, 2011 - BMJ is not allowing to access the critical comments; only full article pdf is accessible).
Danish Cohort study analyzes a group of 723,421 cell phone subscription records in Denmark during the period of 1982 – 1995. The same group was monitored for cancers from 1987-2007.
The major flaw of the study is that the only information about the exposure to cell phone radiation by the study study participants is how long the person owned a mobile phone. The study simply offers no information of actual exposure.
Another major problem of this study is that from the start the cohort of 723,421 cell phone subscribers excluded 200,507 corporate subscribers. This means that the heaviest exposed persons – those who were using cell phones for day-to-day business use - were omitted. It is important to remember that during the 1982 – 1995 period cell phones were expensive for private subscribers, limiting their exposure to possible cancer causing daily use.
The number of flaws in the design of this study, lead to a number of paradoxes.
Paradox #1: Two persons, one of whom spends many hours per week on the phone and the other who spends just a few minutes per week, are analyzed as belonging to the same exposure group when they own the cell phone subscription for the same length of time.
This means that highly exposed and nearly unexposed persons are mixed up in the same exposure group.
Paradox #2: And I quote from the article “…Because we excluded corporate subscriptions, mobile phone users who do not have a subscription in their own name will have been misclassified as unexposed….” It means that the highly exposed corporate users, who did not have personal phone subscriptions (nobody knows how many), have ended up as non-exposed controls.
This is a grave error in the study design that can compared to a scientist performing experiments on living cells in the laboratory and, before measuring results, taking some of the most exposed cells and mixing them with the non-exposed cells and using the mix as a control. Such "preparation" of the control sample, would be condemned and the study deemed as unreliable and unpublishable.
Yet, this is exactly what the Danish Cohort study has done. They “contaminated” the control groups, mixing heavily, and lightly exposed persons. It is difficult to understand how such a flawed study passed through the peer-review of the appointed reviewers and journal editors.
Paradox #3: Any person whose subscription begun after the cut off year of the study (1995) was considered as non-exposed by the “standards” of the study because he/she did not own cell phone subscription before year 1995.
For example, a person who was diagnosed in 2007 with the brain cancer and who had cell phone subscription from 1996 was, by the design of the Danish Cohort study, considered as a non-exposed person who got cancer.
Whereas, in reality, this is a person exposed to cell phone radiation for 11 years who got the brain cancer.
Just based on the above critical evaluation, the Danish Cohort study should never be published in its present form.
But the reality is (still) different and the flawed Danish Cohort study is currently a “valid” peer-reviewed article published on the pages of the British Medical Journal.
It is not uncommon that once discovered, either the journal editors or the authors themselves retract flawed studies. An extreme case of this happened just this year, when the Editor-in-Chief Wolfgang Wagner resigned from Remote Sensing journal after mainstream scientists disavowed the flawed paper published in this journal.
The editors of the British Medical Journal need explain how the Danish Cohort passed the peer-review.
The Editors of the British Medical Journal should immediately withdraw Danish Cohort study.
The conclusions of this flawed-design study are not supportable by the obtained flawed data and the studies conclusions are misleading. They are leading the public to believe that the cell phones are safe, when no such claim can be made based on the Danish Cohort study.
In fact, no reliable scientific conclusion can be drawn from the flawed Danish Cohort study. Which lends us to ask if epidemiologists are misleading us by leading us to believe in something that is not supportable by their study?
Read more from Dariusz Leszczynski in his science blog “BRHP - Between a Rock and a Hard Place” at http://betweenrockandhardplace.wordpress.com Dariusz is a Research Professor at the Radiation and Nuclear Safety Authority in Finland.
Follow Dariusz on twitter: @blogBRHP
Disclaimer: the opinions presented in this column are author's own and should NOT be considered as the official opinions of the STUK - Radiation and Nuclear Safety Authority in Finland.
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