Further critisisms of the flawed BMJ Danish cell phone study
Press Release (excerpt only):
British Medical Journal”ôs Upcoming Cell Phone Study Deeply Flawed, Say Experts
October 20, 2011
Environmental Health Trust and Other Experts Expose Major Flaws
in New Danish Study Claiming No Significant Cancer Risks
from Cell Phone Use.
Link to full press release here
“Unsurprising, biased and misleading,”Ě says EHT President, cancer epidemiologist, Devra Davis, PhD, MPH
JACKSON, WY “” October 20, 2011 EMBARGOED until 23:30 GMT “” A new study to be released online today “Use of mobile phones and risk of brain tumours: update of Danish cohort study,”Ě in the British Medical Journal, claims “to show no link between mobile phone use and tumours.”Ě However, the study is seriously flawed, say technical experts from the U.K., United States, Austria, Sweden and Australia, who have provided critical reviews on the embargoed study to Environmental Health Trust, a research and public educational group and ElectromagneticHealth.org, a health education and advocacy group in the United States.
The study, “Use of mobile phones and risk of brain tumours: update of Danish cohort study,”Ě by Patrizia Frei et al., published online, claims there is no link between long-term use of cell phones and tumors of the brain or central nervous system among 358,403 mostly male cell phone subscribers over the age of 30 during the period 1990-2007. The report is a follow-up to an earlier Danish analysis of the same group when the average use of cellphones was less than a decade that also reported no cell phone-cancer link.
Devra Davis, PhD, MPH, cancer epidemiologist and President of Environmental Health Trust, commented: “From the way it was set up originally, this deeply flawed study was designed to fail to find an increased risk of brain tumors tied with cellphone use. In order for any study of a relatively rare disease like brain tumors to find a change in risk, millions must be followed for decades. By extending an earlier analysis on the same group of cellphone users this new report provides unsurprising, biased and misleading conclusions. It uses no direct information on cell phone use, fails to consider recent and rapidly changing nature of and exposure to microwave radiation from cellphones, cordless phones and other growing sources, and excludes those who would have been the heaviest users””namely more than 300,000 business people in the 1990s who are known to have used phones four times as much as those in this study.”Ě
Highlights of the critique of the BMJ study are below:
The new report misrepresents risk of brain tumors for the very same reason the original Danish study was previously criticized. Removing more than 300,000 cell phone users who were business users from the analysis (almost 30% of the original group), defining as a user anyone making one call a week for 6 months, and ignoring the fact that phone calls were more expensive and shorter years ago, reduces the group”ôs average exposure and makes it very unlikely to find any evidence of increased risk.
Secondly, the report analyzed the rates of brain tumors that occurred between 1990-2007 in those who began using cellphones after 1987, compared to those who were non-subscribers when the study started. This also understates risk, because most of those who began as “ėnon-subscribers”ô to cell phone service (i.e. the “ėcontrols”ô at the time the cohort was collected) became cell phone users later on, and accumulated almost as many years (on average per person) as the “ėexposed”ô subscribers. Hence, the comparison to the population not contained in the subscriber sample is a comparison between two exposed groups. When Michael Kundi and colleagues from the Medical University of Vienna mathematically corrected for this concern in the earlier Danish study, they found a significantly increased risk for brain tumors.
Cell phone users who began using cell phones after 1995 and those under the age of 30 were not considered “ėsubscribers”ô in the study (as with the business users and pay-as-you go users), thus significantly diluting the results and underestimating the risk.
An accompanying editorial on the study by Anders Albom, notes several design limits of this study and repeats a concern raised about this problem in 2005, where he noted:
“Not being able to include corporate users, likely to be among the earliest and heaviest users of mobile phones, also weakens the statistical power of the study.”Ě (See Page 12).
Finally, and importantly, the current, updated Danish study being published today in fact did find increased risk, even though the study is currently being promoted to the media as if it did not. Davis notes,
“Statistical significance tests are tools used in science to help understand the chance that a finding is real. In fact, the article reports a significant increased risk of a very rare form of glioma of the cerebral ventricle based on eight cases (2.58, 1.08-6. 1) but the authors chose to make no mention of this significant finding. In this instance despite the small number the finding is significant.”Ě
“Statistical analyses provide tools, but do not provide rules, for interpreting evidence. This means that findings can be important even when they do not reach significance statistically. In this report, the authors reject all other findings of borderline significance completely. In a study of relatively rare diseases such as brain tumor, the failure to obtain statistical significance should not be confused with a lack of public health importance. In fact, most of the reported numbers of brain tumors in this article give estimated risks where the result goes from below 1 ( a negative result meaning no increased risk), to above 1 (a positive result indicating in some instances a doubled or greater risk).”Ě
“All of the few well-designed case-control studies of this issue have found significantly increased risk. Thus, these borderline findings of increased risk may well signal an important association.”Ě
Commenting further on major flaws in this study, Alasdair Philips, an expert in electromagnetic health from Powerwatch in the U.K., has said of this study”ôs design,
“This study only looks at 7% of the Danish population who had a personal cellphone subscription for at least one year during the period 1987 to 1995. It ignores corporate subscribers (the heaviest users then) and the researchers have no data at all on cellphone use since 1995 so the extra 86% of the population who started to use a cellphone since 1996 were left in the “non subscriber part of the population. This study uses seriously flawed data to make a flawed analysis and should be condemned as misleading spin.”Ě
Camilla Rees, MBA, Founder of ElectromagneticHealth.org and a seasoned campaigner on the issue says,
“This churning of the handicapped Danish cohort study is likely intended to counter the recent WHO IARC classification of cell phone radiation as a Class 2B “ėPossible Carcinogen”ô. The misrepresentation to the media evidenced here parallels the recent misleading CEFALO brain tumor study that purported to show that there is no higher risk of brain cancer in children. In fact, that study did find increased risk of brain tumors in children that the authors dismissed. But, experts in pediatric oncology understand that brain tumors in children could well occur in shorter time periods than in adults. The overlap in investigators in these two studies should also be noted.”Ě (See Careful Analysis of Study Claiming No Brain Tumor Risk from Childhood Cell Phone Use Shows the Abstract and Conclusions Are Misleading)
The writer of the editorial commentary “Mobile telephones and brain tumours”Ě, Ahlbom from Sweden”ôs Karolinska Institute has come under increased scrutiny himself for conflicts of interest.
Mona Nilsson, an investigative journalist from Sweden, has documented a number of these conflicts. Ahlbom recently lost significant credibility when he was dismissed from the WHO”ôs IARC Expert Panel in May. Nilsson reported that he had failed to disclose links to the telecom industry.
“Ahlbom has been a member of the Board of his brother”ôs telecom consulting company, Gunnar Ahlbom AB. He also did not declare his industry affiliation to the Swedish Radiation Protection Authority, where he resigned after this disclosure. Ahlbom is a member of the International Commission on Nonionizing Radiation Protection (ICNRIP), an industry loyal organisation, and participated in setting the ICNIRP radiation exposure limits in 1998. These standards assume that the only biological impact of microwave radiation from cellphones is heat and fail utterly to take into effect non-thermal biological effects thereby greatly underestimating risk.
For the full press release see: http://electromagnetichealth.org/electromagnetic-health-blog/british-medical-journal-study-flawed/Leave a reply →