data As Table 1 shows, the tumour increase is chiefly localized on the habitual-use side of the head (ipsilateral tumours), and is very marked (up to 3-5 times normal incidence) and s.s. for malign brain tumours and acoustic neuromas with cellular phone use, and for astrocytomas and meningiomas with cordless use.
We wondered whether these associations could have a smoothing effect on our modelled results for cordless phone use, so tested a model for tinnitus incorporating both.
The increased risk reported by Söderqvist et al. [ 15] in a study of 15 to 19 year-olds was very similar to that demonstrated for cordless phone use here.
Ordinal logistic regression models were fitted for cellphone and cordless phone use, use of wired or wireless cellphone headset, wireless broadband at home, and the frequency and system of the cordless phone.
In a typical house, non-occupational exposure could come from external sources, such as radio, television (TV), and mobile-phone base stations, as well as internal sources, such as a faulty microwave oven, in-house bases for cordless phones, or use of mobile phones.
The signal is sent over 900 MHz (the same frequency used for cordless phones) and can be sent up to 1,000 feet away, which means that users can hear Rush Limbaugh, MP3's or the sound of a Windows error message from anywhere in their homes or yards.
For cordless phones, no information on regular use was given, only 'ever use', which was reported by 68.8% (n = 242) of the cases and 66.6% (n = 430) of the controls.
The odds ratio of malignant tumour for this age group from cordless phone use was OR 2.1, 95% CI 0.97-4.6 while for digital cellphones it was OR 3.7, 95% CI 1.5-9.1 1.5-9.1
For this reason we restricted our analysis of cordless phone use to the first three years of use.
Secondly, the extent of cordless phone use is positively related to that of cellphone use for calls, both in this study and elsewhere [ 6, 22], so heavy use of one phone type is compounded by heavy use of the other.
There was no statistically significant increased risk for ipsilateral mobile or cordless phone use, for meningioma in the temporal lobe or per year of latency.
