Does frequent mobile phone use increase the risk of brain tumours?
Normal mobile phone use does not appear to increase the risk of brain tumours, but with more than ten years of intensive use there are cautious indications of a slightly elevated risk of glioma. What this means for people who started as children or have been making calls for more than fifteen years has not yet been properly studied.
People who have been making calls for a few years do not need to worry straight away. Several meta-analyses find no increased risk of brain tumours with short-term or average use: the combined odds ratio is around OR 0.98, which amounts to practically no difference compared with non-users. Population-based cancer registries also show no rise in brain tumour incidence, despite the explosive growth in mobile phone use over recent decades.
The picture becomes more nuanced with more than ten years of use. Several meta-analyses find a modest association with brain tumours in general (OR 1.18 to 1.32). These are odds ratios just above 1, suggesting a possible risk increase of roughly 18 to 32 per cent. It should be noted that these are associations, not proven cause-and-effect relationships. Methodological problems, such as retrospective recall bias and inconsistent definitions of 'long-term use', substantially limit the certainty of these findings.
The most concrete signal comes from studies into glioma, a specific type of brain tumour. With more than ten years of use, researchers find an OR of approximately 1.44 for glioma in general. For low-grade glioma specifically, this rises to OR 2.22, although the researchers themselves emphasise that the quality of evidence is low. High-grade glioma, by contrast, shows no increased risk. For meningioma, another common brain tumour, no increased risk has been found with long-term use.
An additional indication that something may be occurring with long-term use is the side of the head on which the phone is held. People who held their phone against one side of their head for decades were found in meta-analyses to have a higher chance of developing a tumour on that same side (OR 1.25 to 1.46 for glioma). This pattern is biologically relevant, but does not yet prove a causal relationship.
The biggest gap in knowledge concerns the long-term situation: what are the risks after more than fifteen years of use, and what does it mean to have started making calls as a child? Reliable data on this are barely available. Given the current generation of children who begin using a smartphone early and intensively, several research groups consider this an urgent question that still needs to be answered.
Based on several meta-analyses of observational studies (case-control and cohort). No experimental or randomised studies are possible on this topic. Main limitations: recall bias, inconsistent definition of 'use', short follow-up duration, and the absence of data on use exceeding 15 years or use during childhood.