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The findings "give a consistent pattern of increased risk for acoustic neuroma and glioma," Dr Lennart Hardell of University Hospital in Orebro, Sweden and colleagues write, with the greatest risk seen on the side of the head where the mobile phone was held.
Acoustic neuromas are benign growths on the nerve linking the ear to the brain, while gliomas are malignant, difficult-to-treat tumours of the brain and nervous system.Concerns have been raised that mobile phones could boost brain tumour risk by exposing the brain to electromagnetic energy, but early studies did not have a long enough follow-up time to fully account for long-term risk, Hardell and his team report in Occupational Environmental Medicine.
Enough time has now passed since mobile phones were introduced to analyse risks of cell phone use for 10 years or longer, which they believe is a "reasonable minimum period" to estimate risk.
2.4 times higher risk
Hardell and his team identified 18 studies of brain tumour risk among long-term cell phone users, 11 of which provided data for 10 years or longer. When the findings were analysed collectively, the researchers found people who used cell phones for at least a decade had a 2.4-fold greater risk of acoustic neuromas and were twice as likely to develop gliomas.
One study found no increased tumour risk with cell phone use, but it did show that mobile phone users who developed brain tumours had larger tumours than non-cell phone users.
"These results are certainly of biological relevance." The greatest risk was for tumours located in the area of the brain with the most exposure and the study periods allowed enough time for tumours to develop, the researchers note.
They add that "longer follow-up is needed, however, as an increased risk for other types of brain tumours cannot be ruled out."
SOURCE: Occupational Environmental Medicine, September 2007. – (Reuters Health)
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