How the study was done: This is the largest health-related case–control study of cell phone use and the risk of head and neck tumors. It was conducted by a consortium of researchers from 13 countries. The data came from questionnaires that were completed by study participants.
What the study showed: Most published analyses from this study have shown no statistically significant increases in brain or central nervous system cancers related to higher amounts of cell phone use. One analysis showed a statistically significant, although modest, increase in the risk of glioma among the small proportion of study participants who spent the most total time on cell phone calls. However, the researchers considered this finding inconclusive because they felt that the amount of use reported by some respondents was unlikely and because the participants who reported lower levels of use appeared to have a slightly reduced risk of brain cancer compared with people who did not use cell phones regularly.4–6
An analysis of data from all 13 countries participating in the Interphone study reported a statistically significant association between intracranial distribution of tumors within the brain and self-reported location of the phone.7 However, the authors of this study noted that it is not possible to draw firm conclusions about cause and effect based on their findings.
Additional analyses of data from Interphone countries
An analysis of data from five Northern European countries in the Interphone study showed an increased risk of acoustic neuroma only in those who had used a cell phone for 10 or more years.8
In subsequent analyses of Interphone data, investigators addressed issues of risk according to specific location of the tumor and estimated exposures. One analysis of data from seven of the countries in the Interphone study found no relationship between brain tumor location and regions of the brain that were exposed to the highest level of radiofrequency radiation from cell phones.9 However, another study, using data from five of the countries, reported suggestions of an increased risk of glioma and, to a lesser extent, of meningioma developing in areas of the brain experiencing the highest exposure.10
How the study was done: This cohort study, conducted in Denmark, linked billing information from more than 358,000 cell phone subscribers with brain tumor incidence data from the Danish Cancer Registry.
What the study showed: No association was observed between cell phone use and the incidence of glioma, meningioma, or acoustic neuroma, even among people who had been cell phone subscribers for 13 or more years.11–13
Million Women Study
How the study was done: This prospective cohort study conducted in the United Kingdom used data obtained from questionnaires that were completed by study participants.
What the study showed: Self-reported cell phone use was not associated with an increased risk of glioma, meningioma, or non-central nervous system tumors. Although the original published findings reported an association with an increased risk of acoustic neuroma,14 this association disappeared after additional years of follow-up of the cohort.15
In addition to these three large studies, other, smaller epidemiologic studies have looked for associations between cell phone use and cancer. These include:
- Two NCI-sponsored case–control studies, each conducted in multiple U.S. academic medical centers or hospitals between 1994 and 1998 that used data from questionnaires16 or computer-assisted personal interviews.17 Neither study showed a relationship between cell phone use and the risk of glioma, meningioma, or acoustic neuroma.
- The CERENAT study, another case–control study conducted in multiple areas in France from 2004 to 2006 using data collected in face-to-face interviews using standardized questionnaires.18 This study found no association for either gliomas or meningiomas when comparing regular cell phone users with non-users. However, the heaviest users had significantly increased risks of both gliomas and meningiomas.
- A pooled analysis of two case–control studies conducted in Sweden that reported statistically significant trends of increasing brain cancer risk for the total amount of cell phone use and the years of use among people who began using cell phones before age 20.19
- Another case–control study in Sweden, part of the Interphone pooled studies, did not find an increased risk of brain cancer among long-term cell phone users between the ages of 20 and 69.20
- The CEFALO study, an international case–control study of children diagnosed with brain cancer between ages 7 and 19, which found no relationship between their cell phone use and risk for brain cancer.21
Investigators have also conducted analyses of incidence trends to determine whether the incidence of brain or other cancers has changed during the time that cell phone use increased dramatically. These include:
- An analysis of data from NCI’s Surveillance, Epidemiology, and End Results (SEER) Program evaluated trends in cancer incidence in the United States. This analysis found no increase in the incidence of brain or other central nervous system cancers between 1992 and 2006, despite the dramatic increase in cell phone use in this country during that time.22
- An analysis of incidence data from Denmark, Finland, Norway, and Sweden for the period 1974–2008 similarly revealed no increase in age-adjusted incidence of brain tumors.23
- A series of studies testing different scenarios (called simulations by the study authors) were carried out using incidence data from the Nordic countries to determine the likelihood of detecting various levels of risk as reported in studies of cell phone use and brain tumors between 1979 and 2008. The results were compatible with no increased risks from cell phones, as reported by most epidemiologic studies. The findings did suggest that the increase reported among the subset of heaviest regular users in the Interphone study could not be ruled out but was unlikely. The highly increased risks reported in the Swedish pooled analysis were strongly inconsistent with the observed glioma rates in the Nordic countries.24
- A 2012 study by NCI researchers25 compared observed glioma incidence rates in U.S. SEER data with rates simulated from the small risks reported in the Interphone study6 and the greatly increased risk of brain cancer among cell phone users reported in the Swedish pooled analysis.19 The authors concluded that overall, the incidence rates of glioma in the United States did not increase over the study period. They noted that the US rates could be consistent with the small increased risk seen among the subset of heaviest users in the Interphone study. The observed incidence trends were inconsistent with the high risks reported in the Swedish pooled study. These findings suggest that the increased risks observed in the Swedish study are not reflected in U.S. incidence trends.
- An analysis of primary brain tumor incidence data (including some of the first benign brain and central nervous system tumor data that SEER began collecting in 2004) reported that the incidence of acoustic neuromas (also known as vestibular schwannomas) was stable (unchanged) from 2004 to 2010.