October 20th, 2011
20 October 2011 – London – A new study published today in the British Medical Journal concludes that mobile phone use does not raise the risk of getting a brain tumour. But scientists and campaigners both in the UK and across the globe have dismissed the study as being seriously flawed and offering misleading and false reassurance to the media and public as to the safety of mobile phones.
The study – Use of mobile phones and risk of brain tumours: update of Danish cohort study – looked at data on the whole Danish population aged 30 and over and born in Denmark after 1925 and subdivided this data into subscribers and non-subscribers of mobile phones before 1995. This was done in order to compare the brain tumour rates within these two groups. The apparent conclusion was that there was no comparative increase in brain tumours among mobile phone subscribers.
Despite this apparently simple and clear-cut conclusion, the Danish study is in fact seriously flawed and misleading according to scientists and campaigners in the UK and the US who have examined the data.
Firstly, the study implies that it is looking at long-term users (which is crucial when looking at the incidence of brain tumours, given the latency lag of about 30 years), when in fact the maximum confirmed use period looked at was only seven years and the minimum was as little as one year.
Furthermore the study excludes business users who were by far the heaviest users in Denmark in the 1990’s. This removed those at highest risk of tumours, severely inflating the apparent risk of non-mobile users with whom they were compared. It also included as ‘non-users’ people who started using mobiles after the study began. Together, these methods distorted the findings by greatly diminishing the difference in risk between mobile users and non-users.
Such are the flaws in the study that Denis Henshaw, Emeritus Professor of Human Radiation Effects, University of Bristol has stated that he “considers the claims in the study to be worthless”. He goes on to comment that: “The researchers misclassified the 88 per cent of the Danish population who started using a mobile phone after 1995. This seriously flawed study misleads the public and decision makers about the safety of mobile phone use. ”
Moreover, the researchers themselves have admitted the analysis is flawed. It states in the report that: “A limitation of the study is potential misclassification of exposure. Subscription holders who are not using their phone will erroneously be classified as exposed and people without a subscription but still using a mobile phone will erroneously be classified as unexposed. Because we excluded corporate subscriptions, mobile phone users who do not have a subscription in their own name will have been misclassified as unexposed. Also, as data on mobile phone subscriptions were available only until 1995, individuals with a subscription in 1996 or later were classified as non-users.”
Epidemiologist Dr. Devra Davis of the Environmental Health Trust in the US says the study is not new, but an extension of a study published by the Danish team two years ago. It was widely criticized at the time and was not considered by the World Health Organization to be reliable when the WHO reviewed the evidence of mobile phone risks and classified phone radiation as a ‘possible carcinogen’ in May 2011.
Lastly, the study is described in the BMJ press release as the largest study of its kind to date, when in fact it is widely recognized by scientists that a cohort study (as opposed to a case-controlled study) despite being ‘big’ is an inappropriate method for studying relatively rare diseases such as brain tumours. This is because there are usually not enough incidents of the disease within the cohort to draw any valid conclusions.
Vicky Fobel, director of MobileWise, a charity advising on mobile phone and health, says: “This study and the press release promoting its findings are misleading the public by implying that phone use has the all-clear. The study only looked at short-term use of mobile phones and by mis-analysing the data has massively underestimated the risks. All the other studies that have looked at the long-term risks have found a link between phone use and brain tumours. This study gives false reassurance and distracts us from the important job of helping the public, especially children, to cut the risk from mobiles.”
MobileWise is shortly publishing a report highlighting the growing body of evidence that points to a link between mobile phone use and a range of health hazards including brain tumours, infertility and DNA damage, and the implications of this for public health policy. The report, endorsed by scientists working in the radiation field, is due to be released in early November
Notes to editors
For further information or to arrange interviews please contact: Tessa Thomas, MobileWise Communications Director, Tel. 020 8888 3600 Mobile: 07796 942 281
Email: Tessa Thomas firstname.lastname@example.org
Use of mobile phones and risk of brain tumours: update of Danish cohort study can be downloaded at: http://press.psprings.co.uk/bmj/october/mobilephones.pdf
MobileWise was set up in 2010 to help children use phones more safely. For more information on MobileWise (www.mobilewise.org) and the Safe Mobile Code. The Safe Mobile Code has been formulated to offer practical solutions for those who want to cut exposure to phone radiation, particularly to the head and groin, which are shown by research to be vulnerable.