Cellular Telephone Use and the Risk of Brain Tumors: Update of the UK Million Women Study

Abstract

Background: The ongoing debate of whether use of cellular telephones increases the risk of developing a brain tumor was recently fueled by the launch of the fifth generation of wireless technologies. Here, we update follow-up of a large-scale prospective study on the association between cellular telephone use and brain tumors.

Methods: During 1996-2001, 1.3 million women born in 1935-1950 were recruited into the study. Questions on cellular telephone use were first asked in median year 2001 and again in median year 2011. All study participants were followed via record linkage to National Health Services databases on deaths and cancer registrations (including nonmalignant brain tumors).

Results: During 14 years follow-up of 776 156 women who completed the 2001 questionnaire, a total of 3268 incident brain tumors were registered. Adjusted relative risks for ever vs never cellular telephone use were 0.97 (95% confidence interval = 0.90 to 1.04) for all brain tumors, 0.89 (95% confidence interval = 0.80 to 0.99) for glioma, and not statistically significantly different to 1.0 for meningioma, pituitary tumors, and acoustic neuroma. Compared with never-users, no statistically significant associations were found, overall or by tumor subtype, for daily cellular telephone use or for having used cellular telephones for at least 10 years. Taking use in 2011 as baseline, there were no statistically significant associations with talking for at least 20 minutes per week or with at least 10 years use. For gliomas occurring in the temporal and parietal lobes, the parts of the brain most likely to be exposed to radiofrequency electromagnetic fields from cellular telephones, relative risks were slightly below 1.0.

Conclusion: Our findings support the accumulating evidence that cellular telephone use under usual conditions does not increase brain tumor incidence.

Figure 1.

Relative risks for brain tumors in users vs never-users of cellular telephones in median year 2001, UK Million Women Study. Results are shown for daily use and ≥10 years use vs never-use only. Results for intermediate categories can be found in Supplementary Table 1 (available online). Relative risks are plotted as squares, with the area of each square inversely proportional to the variance of the log relative risk. Error bars represent the 95% confidence intervals. CI = confidence interval; RR = relative risk.

Figure 2.

Relative risks for brain tumors in users vs never-users of cellular telephones in median year 2001, sensitivity analysis, UK Million Women Study. ^aStratified by year of birth, year of answering the baseline survey, and region only. ^bExcluding women who completed the questionnaire in 1999-2000. ^cExcluding the first 2 years of follow-up. Relative risks are plotted as squares, with the area of each square inversely proportional to the variance of the log relative risk. Error bars represent the 95% confidence intervals. CI = confidence interval; RR = relative risk.

Figure 3.

Relative risks for glioma by location in the brain, in users vs never-users of cellular telephones in median year 2001, UK Million Women Study. Results are shown for ever-use vs never-use only. Results by frequency of use and by years of use can be found in Supplementary Table 1 (available online). ^aTemporal lobe (C71.2) and parietal lobe (C71.3) only. Relative risks are plotted as squares, with the area of each square inversely proportional to the variance of the log relative risk. Error bars represent the 95% confidence intervals. CI = confidence interval; RR = relative risk.

Figure 4.

Relative risks for brain tumors in users vs never-users of cellular telephones in median year 2011, UK Million Women Study. Results are shown for ≥20 minutes talking per week and ≥10 years use vs never-use only. Results for intermediate categories can be found in Supplementary Table 2 (available online). ^aMarked as insufficient if there were fewer than 50 cases in ever-users of cellular phones. Relative risks are plotted as squares, with the area of each square inversely proportional to the variance of the log relative risk. Error bars represent the 95% confidence intervals. CI = confidence interval; RR = relative risk.