Center for Safer Wireless
Promoting Safety in Our Wireless World

Analysis of the INTERPHONE Study - May 24, 2010

The INTERPHONE Study, an international study about the possible link between cell phones and brain tumors, was published in the International Journal of Epidemiology, on Tuesday, May 18, 2010.  This is the largest case-control study of cell phones and brain tumors, including the largest number of users with at least 10 years of exposure and the greatest cumulative hours of use.  The research of this landmark study was completed 4 years ago and, for at least 3 years, scientists have argued over the final conclusions and outcomes.  Despite the extra time, there are many flaws in the results, which is one of the reasons media reports stated the results are inconclusive.

While most media outlets reported that study results are inconclusive, the study reported that regular use of a cell phone of about 30 minutes per day for 10 years on the same side of the head can increase risk of a developing a glioma by 40%.  A glioma is a very aggressive malignant brain tumor that often kills within 2 years of diagnosis.  Both Johnny Cochran and Teddy Kennedy had gliomas and were heavy cell phone users.

Scientists in 13 countries (excluding the United States) studied this issue and contributed to the overall results in this case-controlled study. Scientists surveyed patients who had brain tumors (glioma or meningioma) from 2000 to 2004.  Although the study analysis finds overall no increased risk of brain tumors when looking at all participants in the study, when looking at the subgroup of those participants who used cell phones heavily for a decade or more they had at least a doubled risk of getting a glioma or meningioma (two types of brain tumors).

There is a conclusion in the INTERPHONE study that many readers find misleadingly: “There were suggestions of an increased risk for glioma at the highest exposure levels”. Yet, the data reveal an odds ratio of 1.4 with a 95% confidence interval of 1.03-1.89 and odds ratio for ipsilateral use (talking with a cell phone on the same side of the head) of 1.96 (CI=1.22-3.16) for cumulative call time.  These are clear indications of increased risk for patients in the study with the most exposure.  The results are from hard data.  And that data are consistent with previous studies and meta-analyses by Hardell et al., Kan et al., and Myung et al. showing the same trends.

The study has an Appendix 1 and 2, which are not included when you download the study from the International Journal of Epidemiology but are available on the same website.

Appendix 1: The main INTERPHONE study indicated there was a decreased risk of meningiomas or no effect with cell phone use. However, Appendix 1 showed an 84% increase risk of meningiomas for those who used a digital phone for 1640 hours or more; and for study participants who used both digital and analogue cell phones or if the type of phone used was unknown, a 343% increased risk of meningiomas was shown.

Appendix 2: Because there is a downward bias in the risk estimates caused by participation bias, the team analyzed the lowest reference category for risk estimates (those with the lowest: number of years since first use, cumulative number of calls, and duration of calls) and compared it to the higher categories of use in Appendix 2.  People who used a cell phone for 10 or more years were twice as likely to get a glioma as compared to the controls.  Those who used a cell phone for at least 1640 hours had an odds ratio of 1.82 with a 95% confidence interval of (1.15-2.89), which is an 82% increased risk. This table was originally part of the Interphone paper, but was moved to the appendix as part of the negotiations to reach consensus with the study scientists.   

In an interview with Microwave News, Elisabeth Cardis, who leads the Interphone project said, "To me, there's certainly smoke there,"…"Overall, my opinion is that the results show a real effect." Cardis is with the Center for Research in Environmental Epidemiology in Barcelona.  In another recent interview on Living on Earth, Dr. Cardis said, In my personal opinion, I think we have a number of elements that suggest a possible increased  risk among the heaviest users, and because the heaviest users in our
 study are considered the low users today, I think that's something of concern.”

Some of the members of the INTERPHONE project recently told Microwave News that they now see the risk among long-term users as being larger than when the study began.  Some INTERPHONE scientists think the risk warrants serious attention.

David Carpenter MD MPH, BioInitiative Report co-editor and Director of the Institute for Health and the Environment at University at Albany, Rensselaer, NY says that, “While this study is not perfect, the risks documented in it must be taken seriously as a warning to limit cell phone use, to restrict the use of cell phones, especially by children, and to call on manufacturers for redesign of cell phones and PDAs. It should also serve as a warning to governments that the deployment of new wireless technologies may bring risks to the public that are widespread, involuntary and increase long-term health care costs.”

Concerns with the Study

  • The study is not indicative of today’s cell phone users’ habits
  • The study defined a heavy cell phone user as averaging 2 hours per month. Today, some people talk on cell phones close to 2 hours per day.
  • The study defined a regular user as having only one phone call per week from their cell phone
  • The study was in part funded by the mobile phone industry
  • The study excluded children and young adults – the largest user group of cell phones today
  • Cordless phone use was not mentioned in the study findings, even though participants were asked if they used cordless phones.  (A cordless phone and base emit radiofrequency radiation like a cell phone.)  This is another factor in the equation that likely causes underestimation of risk, since the some of the controls may have used cordless phones which tend to blur the differences between controls and exposed participants. 
  • Though authors of the study describe it as having the largest number of cell phone users with at least 10 years of exposure, only a small fraction (less than 10%) of those people in this study used cell phones for more than 10 years.  
  • Parotid gland tumors and acoustic neuromas were also studied but not reported in the published study.
  • Delays in releasing the final results mean we’ve lost valuable time to react to the findings and make necessary public policy changes.

When there is legitimate evidence of emerging risks to our health that can result in disease and death, people need to know about it, instead of burying it in a large study and labeling it “suggestions of an increased risk”.  People are smarter and have more common sense than scientists believe.  And people in general use different standards when it comes to their children’s health and allowable health risks.

The latency period for brain tumors is 15-30 years.  The latency period is the time interval between exposure to a carcinogen, toxin, or disease-causing organism and development of a consequent disease. Finding increased risk at only 10 years means that some people are experiencing dire health consequences earlier than some scientists projected.  Therefore, learning how to use a cell phone more safely is all the more important to reduce your risk.  (See the top 10 ways to use a cell phone more safely.)

Children are more at risk and vulnerable than adults from the effects of most toxic exposures, including chemicals and radiofrequency radiation from cell phones.  Scientists are concerned about the effects of radiofrequency radiation on the developing brain and nervous system of children.

Our focus should be on educating individuals (especially children) to limit their use of cell phones and how to use them more safely.  In addition, to yield accurate results, we need independent funding of science research on the biological effects of non-ionizing electromagnetic radiation.