SSM perspective
Background
In the past few years, a discussion has been ongoing in both the research community and the media as to whether exposure to radiowaves from the use of mobile phones has an impact on the incidence of brain tumours in the general population. Ever since the introduction of mobile phones in the 1980s, their use has increased dramatically and has now spread to almost all parts of the world. According to the International Telecommunication Union, there were nearly 7 billion mobile phone subscriptions globally in 2014. Because this distribution is so widespread, there is a great need to investigate possible impacts on health. In 2011, the International Agency for Research on Cancer (IARC) gathered experts in the field to form a working group for discussion of the outcomes of relevant studies. The decision was made to classify mobile phones as “possibly carcinogenic to humans” mainly based on indications of an elevated risk of gliomas, a kind of brain tumour.
Sweden is one of the countries where mobile phone use blossomed early on, for which reason incidence trends based on Swedish registries are of pertinent interest in the puzzle of knowledge that needs to be put together to form a solid foundation for risk assessments. However, it is important to keep in mind that this kind of analysis can never prove the lack of, nor the existence of, a correlation. Incidence trends can be influenced by a wide range of factors, apart from direct registry factors (changed coding practice, and the like), in addition to environmental factors and changed lifestyle patterns; other possible aspects are not only protective factors, but also risk factors whose strength is variable over time. Another aspect that should be considered is that some illnesses are characterised by a long latency period. Consequently, they may not manifest themselves until many years after an exposure situation. Nonetheless, it is reasonable to assume that a strong link between radiowave exposure and brain tumour development would have a clear impact on incidence trends within a period of 15 years following large-scale implementation of mobile telephony.
Results
This project initially compiled data from the Swedish Cancer Registry for the purpose of identifying all brain tumour diagnoses made between the years 1980 and 2013, and subsequently estimating the incidences of the brain tumour types of low-grade gliomas, high-grade gliomas, and meningiomas during this period. Also, via Statistics Sweden (SCB), data was collected on these patients’ incomes in order to analyse a possible correlation between income and incidence. It transpired that there was a time lag in the statistics that risked causing substantial underestimation of the number of identified cases in 2013. The findings from the entire period have been taken into account in this report, though the presentation of incidence trend parameters has consequently been limited to the period 1980-2012. In total during the period 1980-2012, 30,255 primary brain tumours were identified on the part of 30,142 patients.
In the case of the meningioma tumours, there was an increased incidence in the age group 0-74. Patients over 75 years of age showed a decrease in the annual incidence. The overall conclusion, based on all the age groups, was that no signicant incidence trend was observed for meningiomas.
The researchers observed a slight decrease in the annual incidence of highgrade brain tumours among patients in the age group 0-39 years, and an increase in the age group 60-74 years of age (p=0.029). On the whole, highgrade brain tumours showed no overall incidence trend.
The outcomes demonstrated a statistically significant decrease in the annual incidence of low-grade gliomas during the period 1980-2012. In terms of age group classification, this significant decrease in low-grade glioma incidence was observed in all age groups above the age of 39. However, these findings should be interpreted cautiously. It is clear that the outcomes largely depend on selecting where the survey begins and ends. Nonetheless, there does not seem to be any long term, upward trend.
No clear difference could be discerned between males and females in terms of incidence trends for all the types of tumours, with the exception of low-grade gliomas (p=0.001). The outcomes from the incidence’s dependency on income are irregular, or rapidly variable, on the part of higher incomes. This indicates an all too low statistical volume and provides no information about possible correlations.
Overall, there was no clear increase in the annual incidence of the studied tumour types from the years 1980-2012, a period of time during which mobile phone use increased sharply. Nevertheless, it should be noted that this study did not investigate a specific correlation between mobile phone use and brain tumour incidence. Many factors have an influence on the development of brain tumours.
All the same, the observation has been made that the presented findings do not provide evidence that any environmental factor encompassing a large proportion of the population (for instance, mobile phone use) has had a material impact on the risk of development of brain tumours between 1980 and 2012.
Relevance
The present report provides support for the previous assessment made by the Swedish Radiation Safety Authority: Exposure to radiowaves while using mobile phones does not pose any significant risks leading to brain tumours. The recommendation to observe precautions by using hands-free equipment during mobile phone calls nevertheless remains in effect, mainly due to longterm uncertainties and indications of biological effects in animal studies.
Need for further research
As this study has only had access to a somewhat complete body of data up to and including 2012, it is strongly recommended to carry out an update. It would be appropriate to launch this kind of study in 2021, with an analysis of statistics up to and including 2017.