Speaker
Dr
Susanna Lagorio
(National Centre for Epidemiology, Surveillance and Health Promotion - National Institute of Health, Rome (Italy))
Description
Over 60 studies on mobile phone use and intracranial tumours in adults have been carried out to date, while one study only has examined this relation in children. This brief overview focuses on malignant brain tumors in adults (labeled “glioma” from the most frequent morphotype).
The 24 studies on glioma risk in adult mobile phone users published by the end of 2011 include 2 cohort studies of mobile phone subscribers, 16 country-specific case-control studies, 3 pooled analyses of published primary studies, and 3 different analyses of the Interphone international study, carried out on the whole data-set from the 13 participating countries, or on data-subsets.
Available studies are far from consistent. Moderate degrees of variation in effect size attributable to heterogeneity are observed in the meta-analysis of risk estimates for ever vs never regular use, as well as for short-term mobile phone use, with combined relative risks around the null value in both cases. The combined relative risk is slightly increased among long-term uses (≥10 years), but the original measures of effect are highly heterogeneous and the finding is entirely attributable to the Örebro study series.
Possible distortions from recall and selection or participation bias complicate the interpretation of findings from case-control studies, while non-differential exposure misclassification is an issue for the subscribers’ cohort studies. Side-validation studies allowed to attribute at least in part the deficits in risk observed in the Interphone studies to participation bias, and the increased risk among heavy users to recall bias and/or systematic exposure error. The exposure index used in the Danish cohort study (subscriber status) was shown to have low sensitivity but very high specificity, which means that the downward bias expected from random exposure measurement error is of minor importance in the analyses of risk in low-prevalence strata such as long-term users.
The increased glioma risks observed in some epidemiologic studies are not compatible with the incidence rates of glioma recorded in the Nordic countries and the US in middle-aged adults (40–59 years) during the past 20 years, assuming induction periods up to 10 years. A modest risk increase among heavy users, on the order of that seen in the Interphone study (40%), cannot yet be excluded, and there are still few data on cancer risk beyond 15 years since start of mobile phone use.
Primary author
Dr
Susanna Lagorio
(National Centre for Epidemiology, Surveillance and Health Promotion - National Institute of Health, Rome (Italy))
