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Posted by on May 17, 2010 in Epidemiology, Neurology

WHO Cell-Phone Study Is Not So Inconclusive

WHO Cell-Phone Study Is Not So Inconclusive

Cell_phone_use.jpg

While some news sources are claiming that the results from WHO’s large INTERPHONE study (yet another study assessing the risk of brain tumors with cell-phone use) are “inconclusive,” a review of the published article, in the International Journal of Epidemiology, generally reveals otherwise. (A press release for the article can also be found here.)

Among dozens of case-control analyses in the study, many of which involved small numbers, few demonstrated an increased odds of meningioma or glioma. Moreover, in the vast majority of cases, the odds of these brain tumors were actually lower with cell-phone use.* On the basis of their results, the authors concluded that there is no increased risk of meningioma among cell-phone users.

When considering glioma, however, the odds were increased among users whose cumulative call time exceeded 1639 hours (OR, 1.40; CI: 1.03, 1.89), regardless of how long they had been using cell phones (1-4 years, 5-9 years, or 10+ years).** The highest cumulative call time was also associated with an increased odds of glioma in the temporal lobe (OR, 1.87; CI: 1.09, 3.22) and on the same side as typical cell-phone use (OR, 1.96; CI: 1.22, 3.16). “Still, the evidence for an increased risk of glioma among the highest users was inconclusive,” the authors wrote, citing several possible sources of study biases, including selection bias. (Unfortunately several news sources evidently grabbed the word “inconclusive” for their provocative ledes.)

The INTERPHONE study was a multinational study, involving 16 centers in 13 countries (Australia, Canada, Denmark, Finland, France, Germany, Israel, Italy, Japan, New Zealand, Norway, Sweden, and the United Kingdom). Between 2000 and 2004, data were collected from people aged 30-59 years, given that these individuals were likely to have a history of significant cell-phone use. The data were compared with information from matched control populations (who, evidently, didn’t use cell phones…ever…! [Addendum “Oops,” see below for a clarification of the control pop). The main analyses included 2409 meningioma cases (2662 matched controls) and 2708 glioma cases (2972 matched controls).

The rationale for studying a possible link between cell-phone use and brain-tumor risk is based on the proposal that low-level exposure to radiofrequency (RF) magnetic fields from cell phones increases the risk of brain tumors that absorb this energy. While cell-phone use has increased dramatically since the time of the study, any risks associated with increased cell-phone use are probably mitigated by lower RF emissions, on average, from newer phones and the prevalent use of texting and hands-free devices (which keeps the RF-emitting cell phone away from the head).

* Use of hands-free devices was excluded.

** However, the confidence interval for the 1-4-year odds ratio was very wide. 

Addendum 10/20/37: The reference or control group, defined as “never regular users,” included those people with meningioma (32% of cases) or glioma (26%) who never had more than 1 call per week, on average, for 56 months. Never users (11% of meningioma cases and 9% of glioma cases) were, in fact, never users.

Yesterday Orac provided another blog-based review of this study, citing the “inconclusive” moniker as accurate. I disagree, given the overall results of the study (and the extent to which any negative study can ever be called conclusive). The only hedge is provided by the high-end cell-phone users for glioma. But even Orac writes, “There was no compelling evidence of an association between cell phone use and either of these cancers.”

Orac also poo-poos the RF rationale for assessing a link between cell-phone use and brain cancer, at least on the basis of DNA breakage. This appears to be an important point to stress (despite the fact that the study was conducted in the first place!).

The INTERPHONE study authors write,

“Much biological research has been done in recent years on possible biological effects of RF fields. This work covers in vitro and in vivo exposure, alone and in combination with other physical or chemical agents, and has found no evidence that RF fields are carcinogenic in laboratory rodents or cause DNA damage in cells in culture. Possible effects of RF fields on other biological endpoints are still being explored.”

The authors cite a white paper from the European Commission, “Health Effects of Exposure to EMF,” which summarizes,

“It is concluded from three independent lines of evidence (epidemiological, animal and in vitro studies) that exposure to RF fields is unlikely to lead to an increase in cancer in humans. However, as the widespread duration of exposure of humans to RF fields from mobile phones is shorter than the induction time of some cancers, further studies are required to identify whether considerably longer-term (well beyond ten years) human exposure to such phones might pose some cancer risk.”

bmartin (1127 Posts)

A native East Tennessean, Barbara Martin is a formerly practicing, board-certified neurologist who received her BS (psychology, summa cum laude) and MD from Duke University before completing her postgraduate training (internship, residency, fellowship) at the Hospital of the University of Pennsylvania in Philadelphia. She has worked in academia, private practice, medical publishing, drug market research, and continuing medical education (CME). For the last 3 years, she has worked in a freelance capacity as a medical writer, analyst, and consultant. Follow Dr. Barbara Martin on and Twitter.