Wednesday, June 13, 2012

Cell Phone Use & Brain Cancer: A Study in Responsible Data Use

An international study links high levels of cell phone use with an increased risk for glioma, one of the deadliest forms of brain cancer.  The study, conducted by an international team of investigators, involved five countries (Australia, Canada, France, Israel and New Zealand) using the Interphone protocol (abstract here).

Compared with never regular cell phone users, those with the highest cumulative call time had a 70% increased glioma risk.  Those with the highest level of radio frequency (RF) exposure over 7 years prior to diagnosis had a 90% increased risk for glioma (odds ratio, OR = 1.91, 95% confidence interval = 1.05 – 3.47) and double the risk for meningioma (OR = 2.01, CI = 1.03 – 3.93), another type of brain tumor.  With cell phone use starting 10 years prior to diagnosis, there was an almost three-fold increase in glioma risk (OR = 2.80, CI = 1.13 – 6.94).  All of these increases were statistically significant. 

This research confirms earlier studies finding increased risk of glioma among cell phone users, with brain tumors occurring in as little as 7 years after exposure.  Some might conclude that children who accumulate high call-time and radio frequency exposures are at especially high risk; they would cite this data to support a ban on cell phone use by children, and limits on adult use.

But is that a legitimate interpretation and application of the data?

The results in the second paragraph above are entirely accurate, but these are only a few of the many ORs that were produced in the extensive study.  The authors put their findings in perspective:

“There were suggestions of an increased risk of glioma in long-term mobile phone users with high RF exposure and of similar, but apparently much smaller, increases in meningioma risk. The uncertainty of these results requires that they be replicated before a causal interpretation can be made.”

The conclusions in the third paragraph above about children are, therefore, hyperbolic and indefensible. While the investigators did find some modest risk, they recommended further investigation, not a cell phone ban.

This study is relevant to tobacco harm reduction in several ways. 

The risk estimates for diseases related to long-term smokeless tobacco use are similar to the risks for cell phones.  As I discussed previously, while smokeless tobacco use cannot be proven to be absolutely safe, risk elevations for cancers (discussed here), as well as heart disease and stroke (here) are modest and usually not statistically significant. 

Elevated risks seen in the Interphone study do not justify the prediction of a cell phone-driven brain cancer epidemic.  That sort of leap for smokeless use, however, is not uncommon.  Surgeon General Antonia Novello in 1992 predicted “an oral cancer epidemic beginning two or three decades from now if the current trends in spit tobacco use continue.” (article here).  Two decades later, we see increased smokeless tobacco consumption, but no oral cancer epidemic.   

While the Interphone study results were consistent with prior research, the investigators did not call for drastic action to prevent cell phone use.  In contrast, questionable findings by the American Cancer Society (discussed here) and the Karolinska Institute (here) have been used to justify a ban on snus in the European Union, and to dissuade American smokers from switching to safer smoke-free substitutes.

The Interphone results suggest that heavy cell phone users might want to consider a “harm reduction” measure: use of a Bluetooth headset. This is comparable to recommending smokeless tobacco use to smokers.  Although there is no evidence that Bluetooth headsets are perfectly safe, they generally operate at lower radiated output power than cell phones, and therefore expose the user’s brain to lower RF doses than do cell phones.

Cell phones, like tobacco, are fixtures of modern society.  Their safe use is informed by responsibly conducted and interpreted epidemiologic studies, and guided by the principles of harm reduction.

1 comment:

The Devil's Thadvocate said...

Great post! It should also be pointed out that cell phones use the same type of rechargeable lithium batteries that are used in SmokefreE-cigarettes that have potential to cause injury if they are misused. Obviously this is not a major risk, but it validates the comparability.