Project

Background: Mobile phone use among adults and children has increased considerably in the past 15 years. This led to concerns in the general public about possible adverse health effects of radiofrequency electromagnetic fields generated by mobile phones. So far, the risk of brain tumors due to mobile phone use has not been addressed in children and adolescents.

Aim: CEFALO is an international case-control study examining the association between mobile phone use and the risk of brain tumors among children and adolescents.

Methods: The study was conducted in Denmark, Sweden, Norway, and Switzerland. All children aged 7 to 19 years and diagnosed with a brain tumor between 2004 and 2008 were eligible for the study. For each patient, two controls of the same age, gender and region of residence were randomly selected from population registries. Exposure data was obtained by personal face-to-face interviews with the study participants and their parents. The frequency and duration of mobile phone use was inquired for various time periods as well as the preferred side of the head. Furthermore, we asked for permission to obtain connection data from mobile phone network operators. The association between mobile phone use and brain tumor risk was evaluated by comparing the duration and intensity of mobile phone use between case patients and controls in conditional logistic regression analyses. Several sensitivity analyses were also calculated.

Results: Overall, 352 patients and 646 controls took part in the study. Participation rates were 83% for cases and 71% for controls. Fifty-five percent of the patients and 51% of controls reported regular mobile phone use (at least one cal per week during at least 6 months). Brain tumor risk was not significantly associated with regular use of mobile phones (Odds ratio [OR]=1.36, 95% Confidence interval [CI]=0.92–2.02). Other exposure metrics such as time since first use or cumulative number and duration of calls were also not significantly associated with brain tumors and not consistent exposure-response relationship was observed. The risk of brain tumors in the regions of the brain that receive most radiation was not associated with regular mobile phone use. Tumors did not occur more often on the ipsilateral compared to the contralateral side. Objective operator data were available for a third of the study participants, who reported to be subscribers. In this subset, brain tumor risk was elevated for participants with the longest period since first subscriptions (> 2.8 years; OR=2.15, 95%-CI: 1.07–4.29). Calculations demonstrated that such a risk, if true, would have resulted in the increase of brain tumor incidence by approximately 50% in the last few years. Such an increase was not observed in Swedish children and adolescents.

Discussion: CEFALO is the first study addressing the possible relationship between mobile phone use and brain tumor risk among children and adolescents. The regression analyses revealed several somewhat elevated risk estimates but none was statistically significant. The pattern of the risk results does not suggest a causal relationship. In most of the analyses, no exposure-response relationship could be observed. Further, brain tumor risk was not elevated in brain regions that are most exposed during calls. Also, brain tumor incidence in children and adolescents in Sweden has rather decreased than increased between 2000 and 2008. In summary, the results of CEFALO do not suggest a causal association between mobile phone use and brain tumor risk. However, since the duration and intensity of use was relatively low in our sample we were not able to evaluate brain tumor risk regarding intensive long term mobile phone use. Given the substantial amount of mobile phone use among adolescents today and the methodological limitations of case-control studies in this research area, incidence trends of brain tumors should be carefully monitored in the next years using high quality registry data.