By Occupational and Environmental Medicine Journal, [RxPG] The findings are based on a sample of over 1400 adults aged between 20 and 80, living in the centre of Sweden. All of them had been diagnosed with a malignant or benign brain tumour between January 1997 and June 2000.
The group were compared with a similar number of healthy adults, matched for age and sex, and living in the same geographical area.
Daily mobile and cordless phone use was assessed, via questionnaire, which included a complete employment history.
How long users spent on the phone had little impact on the probability of being diagnosed with a brain tumour. But where they lived did make a difference for all phone types, and especially for mobile digital phones.
Residents of rural areas, who had been using a mobile digital phone for more than three years, were over three times as likely to be diagnosed with a brain tumour as those living in urban areas.
And digital mobile phone use for five years or more in a rural area quadrupled the risk compared with residency in urban areas.
For malignant brain tumours, the risk was eight times as high for those living in a rural area, but the numbers were small, caution the authors. No such effect was seen for analogue or cordless phones.
The authors reiterate that there is a difference in power output between mobile phones in urban and rural areas. This is because base stations tend to be much further apart in rural areas, requiring a higher signal intensity to compensate.
The compensatory system, known as the adaptive power control or APC, is used for mobile phone (GSM) networks.