October 18, 2004

A Swedish study suggests that people who use a cell phone for at least 10 years might increase their risk of developing a rare benign tumor along a nerve on the side of the head where they hold the phone.

Anders Ahlbom, a researcher behind the preliminary study, said the results were surprising and more research is needed.

Several previous studies have investigated whether the use of cell phones is linked to an increased risk of brain tumors. Although experiments have shown radiation from mobile phones can affect brain cells in a lab, more relevant studies on people have found no evidence that the phones pose a health risk. However, experts have said that because children's brains are developing, it may not be a good idea for youngsters to use the phones for long periods.

The three-year study was conducted by by Ahlbom and Maria Feychting, professor's at the Karolinska Institutet in Stockholm. The study focused on 750 Swedes who had used the cell phones for at least 10 years. The results were published in the International Journal of Epidemiology.

In the study, researchers questioned 150 patients already diagnosed with acoustic neuroma, a benign tumor on the auditory nerve that takes several years to grow before being diagnosed, and 600 who did not have it, about their cell phone use.

All 750 subjects had been using cell phones for at least 10 years, nearly all early analog models that emit more electro-magnetic radiation that the digital models now on the market. Digital phones emit radiation in pulses; the older analog varieties emit continuous waves. Since cell phones increased in popularity in the late 1990's, most of those sold used digital technology.

The risk of developing a tumor was almost double for those who started to use phones before their diagnosis. In addition, the tumor risk was almost four times higher on the side of the head where the phone was held, Ahlbom and Feychting said.

Retrospective questionnaires are not considered the most accurate method of determining a link between behavior and disease. Many links that emerge from such studies turn out not to be true under more rigorous study.

Acoustic neuroma tumors, which can affect hearing, occur in less tha one adult per 100,000 people annually.