Cell phones are not associated with an increased risk of the most common type of brain tumor, finds the first UK study of the relationship between cell phone use and risk of glioma. The results are published online by the British Medical Journal (BMJ) today.

The four year study by the Universities of Leeds, Nottingham and Manchester and the Institute of Cancer Research, London found those who had regularly used a cell phone were not at a greater overall risk of developing this type of tumor.

"Overall, we found no raised risk of glioma associated with regular mobile phone use and no association with time since first use, lifetime years of use, cumulative hours of use, or number of calls," said Professor Patricia McKinney, of the University of Leeds, in a report in the BMJ.

A significantly increased risk was found for tumors which developed on the same side of the head as the phone was reported to have been held but this was mirrored by a decrease in the risk on the opposite side of the head making it difficult to interpret as a real effect.

This finding may be due to people with glioma brain tumors linking cell phone use to the side of the tumor and therefore over reporting the use of a phone on the same side as their tumor. This results in under reporting use on the opposite side of the head, say the authors.

Cell phones have been available in the UK since 1985, but widespread use did not begin until the late 1990s making the number of long term users (over 10 years) quite small. This study had limited numbers for estimating the risk of using a phone over a long period.

Early cell phones were designed to use analogue signals and emitted higher power than current digital phones but the study showed no increased risk of glioma brain tumors with the use of analogue phones.

The study was conducted between 1 December 2000 and 29 February 2004 and included people living in the Thames region, southern Scotland, Trent, the West Midlands and West Yorkshire.

966 people with glioma brain tumors (cases) and 1716 healthy volunteers (controls) were interviewed about their previous cell phone use history including how long they had used cell phones, the number and duration of the calls they made and what make and model of phone they had used.