Following is the abstract of the glioma study ( see previous message by Lloyd Morgan) on the British Medical Journal web site, the link to comments about this study and comments from Alasdair Philips from Powerwatch UK.
Mobile phone use and risk of glioma in adults: case-control study
Sarah J Hepworth 1, Minouk J Schoemaker 2, Kenneth R Muir 3, Anthony J Swerdlow 2, Martie J A van Tongeren 4, Patricia A McKinney 1*
Objective To investigate the risk of glioma in adults in relation to mobile phone use.
Design Population based case-control study with collection of personal interview data.
Setting Five areas of the United Kingdom.
Participants 966 people aged 18 to 69 years diagnosed with a glioma from 1 December 2000 to 29 February 2004 and 1716 controls randomly selected from general practitioner lists.
Main outcome measures Odds ratios for risk of glioma in relation to mobile phone use.
Results The overall odds ratio for regular phone use was 0.94 (95% confidence interval 0.78 to 1.13). There was no relation for risk of glioma and time since first use, lifetime years of use, and cumulative number of calls and hours of use. A significant excess risk for reported phone use ipsilateral to the tumour (1.24, 1.02 to 1.52) was paralleled by a significant reduction in risk (0.75, 0.61 to 0.93) for contralateral use.
Conclusions Use of a mobile phone, either in the short or medium term, is not associated with an increased risk of glioma. This is consistent with most but not all published studies. The complementary positive and negative risks associated with ipsilateral and contralateral use of the phone in relation to the side of the tumour might be due to recall bias.
For comments on this study as listed on the BMJ web site see:
The Comments from Alasdair Philips, for example, are as follows:
“The authors of this paper claim: “Use of a mobile phone, either in the short or medium term, is not associated with an increased risk of glioma.” I do not believe that such a generalised conclusion can be drawn from their data.
The paper states that only 51% of the indentified glioma cases were able to be included in the analysis. 30%, mostly with high grade gliomas, had “died or were too ill to interview”, and the authors admit that “participation rates were higher in those with low grade tumours”. The authors state that they tested for bias, and found none, but fail to present the raw data or the numerical basis for this dismissive claim.
Another concern that I have is that the reference group (used to set the base Odds Ratio at 1.00) not only contained people who had never used a mobile phone but also “non-regular” users and cordless phone users. Since the power output from cordless phones are fixed to about 10mW mean and GSM phones often operate at a lower output that this, people subject to a significant exposure source have been included in the reference group.
The papers analysing Swedish brain tumour data [1,2] show a clear association of brain tumour incidence with at least five years regular use, increasing with ten years use for both mobile and cordless phones. If there is a link to be found, then the effect of including these people in the reference group would have been to skew the dataset and move all the Odds Ratios down towards unity.
As high grade gliomas are often fatal within a short time of diagnosis, it is clear that a prospective study is now needed that will record details of cases as they are diagnosed. The mobile phone operators should be obliged to keep and release phone usage date for such epidemiological analysis – it is not adequate to rely on patients memories as that will greatly reduce the resolving power of any study. As this study was funded jointly by the Government and the Mobile Phone Industry via the Mobile Telephone Health Research group, it is disappointing that it was not more rigorous.”
Director of Powerwatch