Pooled analysis of two case–control studies on use of cellular and cordless telephones and the risk for malignant brain tumours diagnosed in 1997–2003

Objectives: To study the use of cellular and cordless telephones and the risk for malignant brain tumours. Methods: Two case–control studies on malignant brain tumours diagnosed during 1997–2003 included answers from 905 (90%) cases and 2,162 (89%) controls aged 20–80 years. We present pooled analysis of the results in the two studies. Results: Cumulative lifetime use for >2,000 h yielded for analogue cellular phones odds ratio (OR)=5.9, 95% confidence interval (CI)=2.5–14, digital cellular phones OR=3.7, 95% CI=1.7–7.7, and for cordless phones OR=2.3, 95% CI=1.5–3.6. Ipsilateral exposure increased the risk for malignant brain tumours; analogue OR=2.1, 95% CI=1.5–2.9, digital OR=1.8, 95% CI=1.4–2.4, and cordless OR=1.7, 95% CI=1.3–2.2. For high-grade astrocytoma using >10 year latency period analogue phones yielded OR=2.7, 95% CI=1.8–4.2, digital phones OR=3.8, 95% CI=1.8–8.1, and cordless phones OR=2.2, 95% CI=1.3–3.9. In the multivariate analysis all phone types increased the risk. Regarding digital phones OR=3.7, 95% CI=1.5–9.1 and cordless phones OR=2.1, 95% CI=0.97–4.6 were calculated for malignant brain tumours for subjects with first use use <20 years of age, higher than in older persons. Conclusion: Increased risk was obtained for both cellular and cordless phones, highest in the group with >10 years latency period.