A new study from the World Health Organization (WHO) that examined links between mobile phone use and brain cancer risk using data covering 13 countries concluded there is no evidence so far that using mobile phones causes brain cancer: however the researchers urged more studies be done, especially since the data for this investigation does not reflect today’s much higher use of cell phones, and neither does it adequately examine the risk to younger users.

The International Journal of Epidemiology is about to publish the study, which was co-ordinated by the WHO’s International Agency for Research on Cancer (IARC) and conducted by the Interphone Study Group, an international collaboration of 21 academic, public health and industry scientists whose financial independence from the study (some of the funds came, mostly indirectly, from the mobile phone industry) was guaranteed by a “firewall mechanism” provided by the UICC (International Union against Cancer).

Dr Christopher Wild, Director of IARC told the press that while the study did not show an increased risk of brain cancer from using mobile phones, concerns about the heaviest users and changing patterns of use, particularly among young people, means we should continue to do more studies.

Ownership and use of mobile or cell phones has increased rapidly since the early 1980s, when they first appeared on the market, prompting concerns about their impact on health and calls for research to be done.

This study came about because in 1998 and 1999, the IARC coordinated a feasibility study that recommended an international study as the next step.

In their background information the investigators wrote that the cause for concern is the radiofrequency electromagnetic fields that the phones emit.

In a separate statement, they also said that while there have been several other investigations, including case control (comparing users with non users) and cohort studies (following a group of users over several years), none has yet included as many exposed cases, particularly long term and heavy users, as this one.

For this study, which began in 2000, the Group set up a number of case-control studies in 13 countries around the world: Australia, Canada, Denmark, Finland, France, Germany, Israel, Italy, Japan, New Zealand, Norway, Sweden and the UK.

The studies focused on types of tumor that occur in tissue that is known to most absorb radiofrequency energy from mobile phones, and their objective was to look for links between mobile phone usage and tumor incidence.

Also, to “maximize statistical power”, the study focused on tumors occuring in younger people, aged from 30 to 59, as they were the most likely to have been using mobiles the most in the preceding 5 to 10 years, and it also focused on regions likely to have had the longest and highest use of mobiles, such as large urban areas.

The reported results covered cases of glioma (a brain cancer that starts in the cells that support the nerve cells) and meningioma (a tumor that forms in the thin layer of protective tissue that envelops the brain and spinal cord).

Using a common protocol, interviews were completed with 2,708 glioma and 2,409 meningioma patients and matched controls in 13 countries, and after analysing the results the researchers found that:

  • Compared to interviewees who described themselves as never having been regular users of mobile phone, the odds ratio of a regular user developing one of the two types of tumor was actually lower: for glioma OR 0.81; 95% confidence interval CI 0.70-0.94, and meningioma OR 0.79; 95% CI 0.68-0.91.

  • However this reduction was described as “possibly reflecting participation bias or other methodological limitations”.

  • No higher odds ratio was seen in users who had been using mobiles regularly for 10 years or more (glioma: OR 0.98; 95% CI 0.76-1.26; meningioma: OR 0.83; 95% CI 0.61-1.14).

  • Ranking users according to deciles of lifetime number of calls (starting with participants with the lowest 10 per cent usage, then the next, and so on, until the highest ten per cent) showed no elevated odds ratio (all ORs were under 1.0).

  • However, ranking them by cumulative hours of calls showed that the ten per cent heaviest users had a higher odds ratio of developing one of these tumors: OR 1.40 (95% CI 1.03-1.89) for glioma, and 1.15 (95% CI 0.81-1.62) for meningioma.

  • But the researchers were sceptical about this result because the values in this heavy usage group were “implausible” (the 10th decile was equivalent to 51,640 total hours of talking on the mobile phone).

  • As to location of the tumors, the odds of developing a glioma tended to be higher for tumors in the temporal lobe, but the confidence intervals in the odds ratios (ORs) for location of tumor were wide.

  • ORs also tended to be higher among participants who reported using the phone on the same side of their head as the location of the tumor compared to users who reported using it on the opposite side.

The researchers concluded that overall they observed no increase in risk of glioma or meningioma with respect to mobile phone use. Although there was some evidence of an increased risk of glioma among the heaviest users (higher exposure levels), they wrote that biases and errors in the data prevent them from being able to say that the link is causal.

In other words, it appears the evidence of this study is not strong enough to show that heavy use of mobile phones causes these types of brain cancer, even though the data suggests a link.

Thus they recommended that:

“The possible effects of long-term heavy use of mobile phones require further investigation.”

This is particularly important, given that mobile phone usage has changed since the period covered by the study. For instance, in the period covered by the study, the median cumulative call total was about 100 hours, with a median call total time of 2 to 2.5 hours a month. And the cut-off point for the heaviest 10 per cent of users corresponds to about half an hour a day.

Mobile phone usage is more widespread today, and patterns of use have changed. It is not unusual for instance, the researchers told the media, for young people today to be talking on mobiles for an hour or more every day.

Although this higher usage is balanced by lower emissions in the more modern handsets, and patterns of use are moving to include more texting and hands-free operation, nonetheless we need to keep monitoring and investigating the link with health and brain cancer in particular.

The reasearchers said they are continuing with the investigation, and are extending it to include other tumors like those of the acoustic nerve and parotid gland (the largest of the salivary glands). There is also a new project called MobiKids, funded by the European Union, that is investigating the links between brain tumors and mobile phone use in children and adolescents, a group that was not covered by the Interphone study.

In May 2011, the IARC also plan to review the potential cancer-causing effects of mobile phone use as part of its Monographs Programme.

“Brain tumour risk in relation to mobile telephone use: results of the INTERPHONE international case-control study.”
The INTERPHONE Study Group.
International Journal of Epidemiology, 2010;1-20.
DOI:10.1093/ije/dyq079

Source: WHO.

Written by: Catharine Paddock, PhD