BMJ  2006;332:1035-1036 (29 April), doi:10.1136/bmj.332.7548.1035-c

Letter

Mobile phone use and risk of glioma in adults

Conclusions are questionable

EDITOR—The study by Hepworth et al has severe shortcomings, including faulty interpretation and unfounded conclusions.¹ Is there really any occupational or environmental factor capable of inducing glioma in a period of 3 to 4 years (the average duration of use of a mobile phone in this study)? Not even after high doses of therapeutic x rays have such short latencies been observed.^{2 3}

Only 5% of cases had used a mobile phone for 10 or more years. Therefore, induction of glioma cannot be studied. Only an effect on tumour development and growth can possibly be detected. As pointed out,^{4 5} the case-control design is inefficient to study such effects if the duration of exposure is short.

Furthermore, if an effect on an already premalignant lesion is studied only exposures to that region are exposures at all. Therefore the only relevant analysis is that of laterality. And, surprisingly, this analysis resulted in a significantly increased risk that increased further if longer exposure durations were considered. Hence the only analysis compatible with the natural history of the disease and exposure conditions showed a significantly increased risk. But still the authors conclude that the study found no increased risk of developing a glioma associated with mobile phone use. They point to the fact that the odds ratio for contralateral exposure is below 1 and seem to interpret this as an indication for recall bias. However, this is simply a consequence of their method of analysis and of the significant effect on the ipsilateral side.

Institute of Environmental Health, Center for Public Health, Medical University of Vienna, Austria Michael.Kundi{at}meduniwien.ac.at

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Competing interests: None declared.

References

1. Hepworth SJ, Schoemaker MJ, Muir KR, Swerdlow AJ, van Tongeren MJA, McKinney PA. Mobile phone use and risk of glioma in adults: case-control study. BMJ 2006;332: 883-7. (15 April.)[Abstract/Free Full Text]
2. Simmons NE, Laws ER Jr. Glioma occurrence after sellar irradiation: case report and review. Neurosurgery 1998;42: 172-8.[CrossRef][Medline]
3. Kranzinger M, Jones N, Rittinger O, Pilz P, Piotrowski WP, Manzl M, et al. Malignant glioma as a secondary malignant neoplasm after radiation therapy for craniopharyngioma—report of a case and review of reported cases. Onkologie 2001;24: 66-72.[Medline]
4. Kundi M. Mobile phone use and cancer. Occup Environ Med 2004;61: 560-70.[Free Full Text]
5. Kundi M, Hanson Mild K, Hardell L, Mattsson M-O. Mobile telephones and cancer—a review of epidemiological evidence. J Toxicol Environ Health B 2004;7: 351-84.

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Related Article

Mobile phone use and risk of glioma in adults: case-control study

Sarah J Hepworth, Minouk J Schoemaker, Kenneth R Muir, Anthony J Swerdlow, Martie J A van Tongeren, and Patricia A McKinney
BMJ 2006 332: 883-887. [Abstract] [Full Text] [PDF]