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| Authors Hardell
L, Nasman A, Pahlson A, Hallquist A, Mild KH.
This
study examined 209 people with brain tumour, identified from records in
Swedish cancer centres. The patients were diagnosed during 1994-96. Each
subject was matched on sex, age and study region with two controls. In
all, 425 controls were included. Exposure
to cellular telephones, and to other radiofrequencies and chemicals, was
ascertained by postal questionnaire, which was supplemented in some cases
by telephone interview.
Seventy eight cases (37.3%) and 161 controls (37.9%) reported use of cellular telephone. The mean number of hours of phone use for cases was 511 (median 136) and for controls 428 (median 136). The
study found no association
between the occurrence of brain tumours and the amount of cellular phone
use. No association was seen when the number of years of exposure was
considered separately. A "somewhat increased risk" that was
not statistically significant was found for tumours in the temporal
or occipital lobe of
the brain on the same side the cellular phone was used. This was found
only for users of the analogue NMT system. The risk
was 2.56 times greater for the right side and 2.10 for the left side,
but was based on only 7 cases on the right and 5 cases on the left. The
authors state that "the results were based on low numbers and must
be interpreted with caution."
The
main weakness of a case-control
study such as this is that it might be subject to recall bias
i.e. it is more likely that people with a brain tumour remember past cell
phone use compared with controls. The authors state that "validation
of exposure to cellular phones from telephone companies would have been
desirable. However, it turned out to be impossible to get such data."
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