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The international WHO Interphone study was published in May 2010. The results showed an increased risk for malignant brain tumours (glioma) for the heaviest user of mobile phones, (1,640 hours or more in total). The studies on brain tumour risk from the Hardell-group at the University Hospital, Örebro, Sweden have been criticized for seemingly higher risk for mobile phone use than in other studies.
In a new analysis of the results from Örebro it is found that similar results as in Interphone are obtained if restriction of the material and methods is made according to the WHO study. The results are now published in International Journal of Epidemiology on Internet.
The WHO Interphone study included only persons diagnosed with brain tumour at the age of 30-59 years. Use of cordless desktop phones (DECT) was not assessed. Furthermore, the highest exposure group was restricted to persons who had used a mobile phone for 1,640 hours or more in total. That corresponds to only 30 minutes per day over a time period of 10 years.
On the contrary, the Örebro studies included patients with brain tumour aged 20-80 years. Use of cordless phone was surveyed as carefully as use of mobile phone. The group with highest exposure included persons who had used a mobile phone more than in Interphone; 2,000 hours or more.
The Örebro group has now in the new paper restricted the analysis to the criteria used in the WHO study. Only patients and control subjects aged 30-59 years were included, use of cordless phone was disregarded and highest exposure was limited to 1,640 hours or more. Thereby the risk for glioma was lowered from odds ratio (OR) 2.31 to OR 1.75 in the most exposed group. The corresponding result in Interphone was OR 1.41. Similar results were found in both studies for tumours in the most exposed area of the brain (the temporal lobe), but now it is Interphone that gives a higher risk, OR 1.87, compared with OR 1.46 in the Örebo study.
Besides similar results in both studies when the same criteria are used, this analysis confirms the critique of the Interphone study. The risk has been underestimated since persons aged 20-29 years and more than 60 years of age were excluded, use of cordless phones was not assessed and risk for the most exposed persons was not analysed.
In conclusion both studies showed a statistically significantly doubled risk for glioma at the same side as the mobile phone had been used for 1,640 hours or more; Örebro study OR 2.18, Interphone OR 1.96. Simlar results were thus obtained in both studies if the same criteria were used in the analysis, that is type of phone (only mobile), cumulative number of hours for use, age group, and anatomical localisation of the brain tumour compared with exposure to microwaves from the mobile phone.
Lennart Hardell, Professor, Department of Oncology, University Hospital. SE-701 85 Örebro, SwedenPhone + 46 19 602 10 00, E-mail: firstname.lastname@example.org
Kjell Hansson Mild, Professor, Department of Radiation Sciences, Umeå University, SE-701 87 Umeå, Sweden
Phone + 46 90 7858487, E-mail: email@example.com
The Interphone Study Group. Brain tumour risk in relation to mobile telephone use: results of the Interphone international case-control study. Int J Epidemiol 2010;39: 675–694.
Hardell L, Carlberg M, Hansson Mild K. Re-analysis of risk for glioma in relation to mobile telephone use: comparison with the results of the Interphone international case-control study. Int J Epidemiol 2010; doi:10.1093/ije/dyq246
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