UK / USA: Misleidende studie met verouderde data over mobiel bellen in Scandinavie.
vrijdag, 21 oktober 2011 - Categorie: Berichten Internationaal
In het toonaangevende British Medical Journal verscheen op 21 okt. 2011 een artikel met de titel: ''Use of mobile phones and risk of brain tumours: update of Danish cohort study'' met als auteurs Patrizia Frei, Aslak H Poulsen, Christoffer Johansen, Jorgen H Olsen, Marianne Steding-Jessen, and Joachim Schuz.
De auteurs komen tot de conclusie dat er geen verschil te zien is tussen bellers met mobiele telefoon en niet bellers wat betreft het risico op hersentumoren.
De studie wordt door wetenschappers en actievoerders ''misleidend'' genoemd, onder meer om de volgende redenen:
De gebruikte data stammen van voor 1995, sluiten mobiel bellen voor zakelijk gebruik uit (juist de mensen die het meeste bellen) en betrekken alleen personen boven de 30 jaar bij de onderzoeksresultaten.
Bovendien wekt de studie de suggestie dat gekeken is naar langetermijn effecten (nodig bij een mogelijke latentietijd van 30 jaar bij hersentumoren) terwijl de gemiddelde gebruiksduur in het cohort op 7 jaar ligt!
Ondertussen hebben de spindoctors van Big Telecom hun doel bereikt, de grote Engelse kranten nemen de conclusie van de studie klakkeloos over zie bv: www.dailymail.co.uk/health/article-2051515/Mobile-phones-DONT-raise-risk-brain-cancer-says-largest-study-far.html .
Leest u onderstaand de Engelstalige commentaren van Powerwatch en Mobile News:
Bron: Powerwatch 21 okt. 2011:
This misleading study has many flaws and serious confounders and should not give anyone reassurance that mobile phone use is not associated with an increase in brain tumours. In our opinion the paper should not have been published in this form � it should have failed peer-review. We recommend that it is disregarded as low quality science.
Denis Henshaw, Emeritus Professor of Human Radiation Effects at the University of Bristol agrees with this view: ''This seriously flawed study misleads the public and decision makers about the safety of mobile phone use. I consider that their claims are worthless.''
What the BMJ Press Release says:
''There is no link between long-term use of mobile phones and tumours of the brain or central nervous system, finds new research published on bmj.com today. In what is described as the largest study on the subject to date, Danish researchers found no evidence that the risk of brain tumours was raised among 358,403 mobile phone subscribers over an 18-year period.''
What do we see as the main problems?
The researchers have no data at all on mobile phone use since 1995.
The extra 88% of the population who started to use a mobile phone after 1995 are placed in the ''non user'' part of the population. They also assumed that anyone having at least a one-year a mobile phone contract in the period 1987 to 1995 will have continued to have one up to 2007. That will seriously damage and distort any data analysis.
It did not analyse corporate subscribers (the heaviest users in the 1987-1995 period).
In total this placed 36% of total users from that period in the ''non-users'' group of the general population.
They did not control for cordless phone use.
This is despite the first author (Frei) having published a paper showing that a third of a person's microwave exposure can come from cordless phone use (with another third from mobile phone use and the other third from base stations and other UHF transmitters). Professor Lennart Hardell has repeatedly shown increases in brain tumours associated with extensive cordless phone use - any such cases would occur in the ''non-users'' group and reduce any effect in the cohort group.
The new paper admits (our emphasis):
''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.''
The IARC panel of 30 scientists who judged RF exposure as a Class 2B possible human carcinogen in May 2011, commented on the 2006 paper of the Danish Cohort study: ''In this study, reliance on subscription to a mobile phone provider, as a surrogate for mobile phone use, could have resulted in considerable misclassification in exposure assessment.'' Lancet, 22 June 2011
Pre-1995 almost all these subscribers used analogue mobile phones which operate quite differently to GSM and 3G handsets used since 1995. Analogue mobile phones were slightly higher powered but did not pulse in the way GSM phones do.
This study only looks at 7% of the Danish population who had a personal mobile phone subscription for at least one year during the period 1987 to 1995. They had few women subscribers in their cohort - that is unfortunate as the cohort does not reflect the general populataion mobile phopne use. In this analysis they have 6% of the Danish population as male mobile phone users and only 1% as female mobile phone users.
They lost 37,093 people from the user cohort because their either died or emigrated. This represents a loss of almost 10% of the current cohort of 358,403 people.
Voor het origineel met onderliggende noten zie:
Mobile News rapporteert via EMFats op 21 okt. 2011 als volgt:
From Vicky Fobel, director of MobileWise:
20 October 2011, London. A new study published today in the British Medical Journal (embargoed for 11.30 pm tonight) 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 Davies 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 criticised 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 recognised 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 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 and the Safe Mobile Code www.mobilewise.org 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.
Voor het origineel zie:
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