Hardell L, Carlberg M. (2009).
phones, cordless phones and the risk of brain tumours. International Journal of Oncology. 35(1): 5-17.

Rapid increases in the use of wireless phones in the past decade have raised concerns about potential adverse health effects, including an increased risk for brain tumors.  The ipsilateral brain (same side as the mobile phone has predominantly been used) is most exposed; whereas the contralateral side is less exposed.  Previous studies have been hampered by the short latency period, as cancers generally take decades from first exposure to manifest.  Sweden was one of the first countries to adopt wireless phone technologies, making it an ideal study site.

The authors of the current study have published 3 previous case-control studies on this topic.  The objective of the current publication was to report further analyses of the latter two studies.

The second case-control study included cases diagnosed between January 1, 1997 and June 30, 2000 and population-based controls.  Use of wireless phones, including the side of the head on which the phone was typically held, was assessed by a self-administered questionnaire, a supplementary phone call, and a follow-up letter.  Tumor localisation was defined using medical records.  Cumulative hours of use were calculated based on the first and last year for use and the average number of minutes per day during that time period.  The second case-control study included 1,429 cases and 1,470 controls.  The third case-control study used identical methods as the second study.  The study period was from July 1, 2000 until December 31, 2003.  In total, 729 cases and 692 controls participated.  The current analysis is based on the pooled samples from these studies.

The risk of astrocytoma grade I-IV was significantly increased when overall mobile phone use was considered (OR=1.4, 95% CI 1.1-1.7).  The odds ratio increased to 2.0 (95% CI 1.5-2.5) for ipsilateral use.  Using >10 year latency time yielded higher ORs.  The highest odds ratio for astrocytoma was found among those who initiated mobile phone use before age 20 (OR=5.2, 95% CI 2.2-12).  In this group, the OR was even higher for ipsilateral use (OR=7.8, 95% CI 2.2-28).  Similar results were found for use of cordless phone.  No significantly increased risks were observed for oligodendroglioma and other/mixed glioma.  Considering benign brain tumors, use of mobile phones increased the risk of acoustic neuroma (OR=1.7, 95% CI 1.2-2.3), as did the use of cordless phones (OR=1.5, 95% CI 1.04-2.0).  These OR increased further for ipsilateral use whereas no significantly increased OR were found for contralateral use.  The highest risk was found for those who first use mobile phones before age 20 (OR=5.0, 95% CI 1.5-16), with odds ratios increasing to 6.8 (95% CI 1.5-35) for ipsilateral use.  Results were also calculated for meningioma and other benign brain tumors, although most odds ratios were not statistically significant. Gender-specific analyses for astrocytoma and acoustic neuroma showed no differences in risk by gender.

Interpretation and Limitations
The main results are consistent with an increased risk for ipsilateral astrocytoma and acoustic neuroma for use of both mobile and cordless phones.  Especially worrying is the increased risk in persons with first use before age 20 years.  The findings of this study are consistent with the hypothesis that microwaves disrupt blood brain barrier function so that carcinogenic substances may leak into the brain, exposing astrocytes in particular.

The authors report a consistent association between use of mobile or cordless phones and astrocytoma and acoustic neuroma.

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