Background: There remains controversy as to whether cell phones cause cancer. We evaluated whether temporal changes in cell phone use and the incidence of glioma in Canada were consistent with the hypothesis of an increased risk.
Design: We used data from the Canadian Cancer Registry to calculate annual incidence rates for glioma between 1992 and 2015. The annual number of new cell phone subscribers was determined using national industry statistics. The number of newly diagnosed gliomas was compared to the predicted number by applying risks from epidemiological studies to age-specific population estimates. Specifically, we calculated the "predicted" number of incident gliomas by determining the annual prevalence of cell phone users and years of use. These estimates were multiplied by the corresponding risk estimates to determine the predicted number of gliomas.
Results: The number of cellular subscriptions in Canada increased from nil in the early-1980s to approximately 29.5 million in 2015. In contrast, age-standardized glioma incidence rates remained stable between 1992 and 2015. When applying risk estimates from i) a recent pooled analysis of Swedish case-control studies, ii) the 13 country INTERPHONE study, and iii) more recent results from data collected from the Canadian component of the INTERPHONE these risks overestimated the observed number of glioma cases diagnosed in Canada in 2015 by 50%, 86%, and 63%, respectively.
Interpretation: Predictions of glioma incidence counts using estimates of the relative risk of glioma due to cell phone use from case-control studies over-estimated the incidence rates of glioma in Canada. The absence of an elevation in incidence rates of glioma in conjunction with marked increases in cell phone use suggests that there may not be a causal link between cellphones and glioma.
Keywords: Brain cancer; Cell phone use; Glioma; Radiofrequency fields; Time-trend study.
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