Hardell L, Carlberg M, Mild KH (2005):

The authors have published several papers based on a case-control study carried out in Sweden. They included patients aged 20-80 years with brain tumour, diagnosed between January 1997 and June 2000 in the middle part of Sweden. Initially each patient was matched with a control, but in later analyses, including this one, all cases (n=1429) and controls (n=1470) who answered a questionnaire were included. Use of a cell or cordless phone was assessed. The authors decided to analyze their data with the subjects grouped according to place of residence. They did this because a recent study had reported that there is a difference in power output from mobile phones between urban and rural areas. Hardell and colleagues were able to take advantage of the fact that the Swedish population register includes information on the present municipality for all residents. The municipalities are classified into six categories depending on the population density, and the number of inhabitants in the nearest vicinity of the main city in that municipality. H1 and H2 are the highest density categories, and H6 the lowest.

There are multiple analyses reported in the paper. They are divided into groups of analogue, digital, and cordless phones and odds ratio (OR) calculations are given for exposed and unexposed subjects living in different areas. There are a number of statistically significant Ors reported. The authors state that the results are most pronounced for digital phones. Living in a rural area gave an odds ratio for use of a digital phone of 1.4 (CI 0.98-2.0), increasing to 3.2 (CI 1.2-8.4) for those with more than 5 years latency. The latter result is based on 17 cases and 6 controls. The authors also state that the effect was most obvious for malignant brain tumours, but their calculation was for 10 cases and only one control.

Hardell et al. state

"In future studies, place of residence should be considered in assessment of exposure to microwaves from cellular telephones".



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