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No increase in the risk of brain tumours in children and adolescents as a result of using of mobile communications devices

Expert opinion of the BfS on the international MOBI-Kids study

  • The MOBI-Kids study investigated the relationship between brain tumours and wireless phone use in a collaborative analysis of data from 14 countries.
  • With almost 900 children and adolescents with brain tumours and 1900 children and adolescents without brain tumours, this is the largest study to date on mobile phone use and brain tumours in this age group.
  • The results of the study suggest that the use of mobile or cordless phones does not increase the risk of brain tumours in adolescents.
  • A supposed decrease in the risk of brain tumours the longer and more often mobile communication devices were used as observed in the study indicates a possible methodological artefact because there is no reason to assume an actual protective effect. The authors assume that the reasons for the observed effect are uncertainties in the information on use (if it came from the parents instead of the children and adolescents themselves) and changes in the usage behaviour of persons with the disease even before the diagnosis.
  • Because of possible sources of bias, which may be present in case-control studies despite the utmost care and effort, a small increase in risk cannot be completely ruled out even based on the results of this study. However, overall, the observations of the study clearly speak against a substantially increased risk of brain tumours in children and adolescents as a result of using mobile and wireless phones.
  • The study supports the current scientific view that there is no robust scientific evidence that mobile phone radiation increases the risk of brain tumours.

Background

Mädchen mit Smartphone Mädchen mit SmartphoneSource: byswat/Stock.adobe.com

Wireless communication technologies such as mobile phones or wireless DECT phones are a central part of our lives. This now also applies to children and adolescents, especially with respect to mobile communications.

Mobile phones and wireless DECT phones are sources of both high- and low-frequency magnetic fields. These are classified as “possibly carcinogenic” (Group 2b) by the World Health Organisation (WHO). Such a classification by the IARC means that such a risk is not probable but cannot be excluded because of individual indications.

In the case of mobile phones and DECT phones, the question of a possible risk for brain tumours arises above all because exposure is strongest in the head area. If such a risk existed, children and adolescents in particular could be affected. On one hand, the developing brain of children and adolescents is particularly sensitive. On the other hand, children and adolescents can be subjected to such exposure for a particularly long time if they start use these technologies from an early age.

The scientific investigation of whether using a mobile phone or DECT phone increases the risk of brain tumours in children and adolescents is a particular challenge. Brain tumours fortunately occur only rarely in children and adolescents. However, meaningful results can be expected only from a study with many brain tumour cases. Therefore, case-control studies are often conducted for this purpose.

However, from a purely methodological point of view, it is difficult to obtain reliable information on usage behaviour retrospectively because all participants have to remember their behaviour. In some cases, this goes back many years. However, if these limitations are taken into account in an adequate manner, scientifically robust statements can still be derived from carefully planned and correctly conducted case-control studies such as this one. In general, the overall picture that emerges from the different types of studies is always relevant for the risk assessment.

Patients from 14 countries were included in the MOBI-Kids study. Results of the study on the relationship between the use of mobile and DECT phones by children and adolescents and their risk of brain tumours were published in Environment International at the end of December 2021 (Castaño-Vinyals et al. 2021). The MOBI-Kids study was mainly funded by the European Commission (grants 226873 and 603794); partial funding for the German project was provided by the Federal Office for Radiation Protection as part of Departmental Research Project 3609S30010 (duration: 2010–2014).

Study designShow / Hide

The case-control study was conducted in Australia, Austria, Canada, France, Germany, Greece, India, Israel, Italy, Japan, Korea, the Netherlands, New Zealand, and Spain in multiple hospitals per country.

Castaño-Vinyals et al. compared the usage behaviour of children and adolescents who had a brain tumour between the ages of 10 and 24 with that of children and adolescents who did not have a tumour (i.e. the controls). In the study the brain tumour cases had been either diagnosed histologically or confirmed by imaging. Recruitment took place directly in the neurological or neurosurgical departments of the participating hospitals between 2010 and 2015. The controls were patients undergoing treatment for appendicitis during the same period. For each brain tumour case, two controls matched for age, sex, and interview period were included.

Information on the duration and frequency of use of mobile phones and DECT phones was collected in personal questionnaire-based interviews. The reliability of such interview data was tested in an additional study. In this study, the usage behaviour of controls and participants from the general population was recorded over a period of four weeks using a smart phone app and compared with data from the questionnaire. In addition, for about one quarter of the cases and the controls, data on mobile communications use were requested from the respective mobile communications provider.

The evaluation used both usage behaviour (time since first use, total number and total duration of phone calls) and an estimate of how much exposure the head was subjected to. This was summed up over the service life. The evaluation took into consideration the educational status of the parents as a measure of the influence of socio-economic factors. In addition to the main analyses, Castaño-Vinyals et al. checked the robustness of their results in various sensitivity analyses.

ResultsShow / Hide

The participation rate in the study was 72 % for cases and 54 % for controls (in each case relative to all patients approached in the hospitals). Data from 899 cases and 1910 controls were included in the evaluation. Because the different types of brain tumours in children and adolescents differ greatly in biological terms, they were evaluated separately in the study. The main evaluation is based on neuroepithelial tumours, which accounted for 76% of the tumours in the study.

In case-control studies, the odds ratio is calculated as a measure of risk. In the case of rare diseases such as brain tumours, this roughly corresponds to the ratio between the probability of disease in exposed individuals and the probability of disease in non-exposed individuals. If the odds ratio is equal to 1, the risk of disease for exposed and non-exposed individuals is exactly the same (i.e. exposure has no influence on the risk of disease). If the odds ratio is greater than 1, the risk for exposed individuals is greater than for non-exposed individuals. If the odds ratio is less than 1, the risk for exposed individuals is less than for non-exposed individuals. For regular users of mobile or DECT phones, the odds ratio for neuroepithelial tumours was 0.85 (95 % confidence interval: 0.62–1.18). This means that in the study, the risk of developing a brain tumour tended to be lower for regular users of mobile and DECT phones than for non-users. The odds ratio also tended to decrease with the intensity and duration of use, especially for 15–19 year olds.

This pattern of results was evident when looking at both the usage behaviour and the measure of field exposure to high- and low-frequency magnetic fields at the head. A separate evaluation for mobile phones and DECT phones each yielded a similar result as did the separate consideration of different subtypes of neuroepithelial brain tumours (e.g. gliomas). However, for the temporal lobe tumour group, there was evidence of an increase in odds ratios with time since first use among 10- to 14-year-olds as well as of an increased risk with wireless phone use for at least 10 years among 20- to 24-year-olds. However, this evaluation is based on extremely small case numbers, and the confidence intervals for the odds ratios are quite wide. This means that the risk was estimated only imprecisely and that the result may have been strongly influenced by random fluctuations and are thus not particularly reliable.

The fact that the odds ratios determined in the study are largely smaller than 1 indicates a certain bias in the results because there is no reason to assume a protective effect through the use of mobile phones and DECT phones. According to the authors, this underestimation could have several causes. One possible cause could be that parent-reported information on usage was more frequent for cases than for controls and that parents often underestimated the intensity of use. Castaño-Vinyals et al. state that especially in the group of 15–19 year olds for whom the odds ratios decreased most noticeably with the intensity of use, the interviews were partly conducted only with the parents for the cases. If only interviews conducted with the afflicted individuals themselves (alone or together with the parents) are considered in the analysis, the odds ratios are much closer to 1 than in the overall evaluation.

Another possible cause is that the usage behaviour of individuals suffering from a brain tumour might have changed because of symptoms that occurred before the diagnosis. This is consistent with the fact that the odds ratios increase if the use data from the five years prior to the time of diagnosis are not taken into account. This suggests that symptoms that occurred in the cases in the five years prior to diagnosis and which reduced the intensity of use could play a role in the possible underestimation of risk in the overall evaluation.

Overall, according to the authors, the study does not provide evidence for a causal relationship between the use of wireless phones and brain tumours in children and adolescents. A small increase in risk cannot be completely ruled out because of possible remaining biases.

Assessment

The study by Castaño-Vinyals et al. has a number of strengths compared with previously existing studies on the topic. The study size is considerably larger than in the only case-control study on the association between mobile phone use and brain tumour diseases in children and adolescents that exists to date: the CEFALO study (Aydin et al. 2011). This included 352 cases and 646 controls from four countries (Denmark, Sweden, Norway, and Switzerland) and had shown a non-significant increased risk. In addition, the average duration and frequency of use in the MOBI-Kids study are considerably greater than in the CEFALO study. A relationship between mobile phone use and brain tumour risk (if one even existed) would thus have been more likely in the MOBI-Kids study than in the CEFALO study.

The proportion of long-term users (> 10 years) is even higher in the MOBI-Kids study (22.5 %) than in the INTERPHONE study (13.6 %) conducted on adults (INTERPHONE Study Group, 2010). The MOBI-Kids study thus has a more meaningful database than previous studies. With the widespread introduction of new mobile phone technologies, the average transmission power of mobile phones has been considerably reduced. While exposure in the INTERPHONE study was mainly through 1G (C-network) and 2G (GSM) phones, phones with the much more efficient 3G (UMTS) standard were available to the users in the MOBI-Kids study. With the same usage behaviour, a lower exposure of the participants in the MOBI Kids study must therefore be assumed.

Other strengths of the study are that the use of wireless phones was also taken into account and that the evaluation was additionally carried out with a measure of estimated field exposure at the tumour site (Calderón et al. 2022).

Another positive aspect of the study is that in an additional study, it was examined whether the quality of the questionnaire data differed between cases and controls by comparing the questionnaire data with the data provided by the mobile communications providers. Such a difference would lead to a bias in the results. However, there was no relevant difference.

Despite the comparatively large study size, the case numbers in various subgroups are also quite small in this study. Meaningful evaluations for these subgroups are thus not possible, or their results are rather imprecise. Weaknesses of the study (which apply to practically all case-control studies) are that a certain bias of the results as a result of different willingness of cases and controls to participate depending on their usage behaviour (selection bias) cannot be ruled out and that the information on usage behaviour was collected retrospectively. In contrast to case-control studies, cohort studies do not have the problem of selective willingness to participate. It is also possible to continuously collect information on use behaviour. However, cohort studies are considerably more elaborate than case-control studies. The COSMOS study is an ongoing long-term cohort study with 300,000 participants from six countries (the Netherlands, England, Sweden, Finland, Denmark, and France) (Schüz et al. 2011). Results are not yet available.

The results of the MOBI-Kids study support the results of existing studies on adults, most of which found no increased risk for the occurrence of brain tumours depending on mobile phone use. The only study to date on mobile phone use and brain tumours in children and adolescents (Aydin et al. 2011) showed no statistically significant relationship. However, the study looked at much smaller numbers of cases. The duration of use was also much shorter than in the MOBI-Kids study.

Summary

So far, there is no scientific evidence of a causal relationship between mobile phone use and the risk of brain tumours in children and adolescents as explained in the position on the subject 5G (in German only). The results of the MOBI-Kids study also provide no indication of a corresponding relationship. The large, carefully conducted multi-centre study thus contributes to reducing existing uncertainties regarding the health risk to children and adolescents as a result of using wireless phones.

LiteratureShow / Hide

Aydin, D., et al. (2011). "Mobile Phone Use and Brain Tumors in Children and Adolescents: A Multicenter Case-Control Study." Journal of the National Cancer Institute 103: 1-13.

Calderón C, Castaño-Vinyals G, Maslanyj M, et al. Estimation of RF and ELF dose by anatomical location in the brain from wireless phones in the MOBI-Kids study. Environ Int. 2022;163:107189. doi:10.1016/j.envint.2022.107189

Castaño-Vinyals, G., S. et al. (2021). "Wireless phone use in childhood and adolescence and neuroepithelial brain tumours: Results from the international MOBI-Kids study." Environ Int 160: 107069.

INTERPHONE Study Group, 2010. Brain tumour risk in relation to mobile telephone use: results of the INTERPHONE international case-control study. Int. J. Epidemiol. 39, 675–694.

Schüz, J., P. et al. (2011). "An international prospective cohort study of mobile phone users and health (Cosmos): design considerations and enrolment." Cancer Epidemiol 35(1): 37-43.

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