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 and we asked for permission to obtain connection data from mobile phone network operators.
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 call 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. The database was further used to evaluate many potential risk factors (see publication list).
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. 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.