Lloyd Morgan's Column

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Commentary - Mobile phone use and risk of glioma in adults: case-control study

(Hepworth et al., BMJ 19 January 2006)

In years past, this paper would never have been published because such a low participation rate of cases and controls would have, by itself, been a cause for rejection. With only 51% of glioma victims (30% had died by the time they were contacted) and 45% of the controls (29% refused to participate) participating, combined with more affluent controls than cases, there is little reason to believe any of the reported results.^[1]

The study would seem to suggest that using a cellphone would protect the cellphone use from the risk of glioma. If there is no risk of glioma from cellphone use, then there would be about the same number of odds ratios greater than one (increased risk) as there would be odds ratios less than one (reduced risk). Overall this study reports 34 odds ratios greater than one to 8 odds ratios less than one. This is equivalent to saying if I flip a coin 42 times, what is the chance that I will get 34 heads and 8 tails. Such a probability can be calculated. The probability that cellphone use protects the user from glioma is 99.997%.

There are only two possible conclusions. Either a cellphone use protects the user from glioma or the study is flawed. You, the reader, must choose between these two possibilities. There is no other choice possible.

In spite of these incredible flaws, the study did report a 60% increased risk of glioma for regular cellphone use of 10 years or more on the same side of the head as the location of the tumor. Another study has found similar results, though with much higher risk of glioma.^[2]

The reference group for this study's findings is "Never/non-regular" cellphone users. Because this reference group did not exclude the users of cordless (DECT) phone the reference group cannot be describe as unexposed. Hardell et al. had reported that cordless phone users who did not use cellphone are at risk of high-grade astrocytoma (OR=1.9, CI; 1.01-3.5).^[3]

Finally, it is important to understand that this study, as is true with every Interphone study, has received substantial funding from the cellphone industry. Though the study reports that this funding "ensures complete independence for the scientific investigators," this is inherently not possible. Researchers careers are dependent on receiving research grants. Even with isolation of funding for a specific study from the researchers themselves, the conflict-of-interest in such funding is not resolved. Because the researchers know where the funding has come from, the old adage, "Don't bite the hand that feeds you" becomes the effective psychological reality (whether conscious or unconscious).

This same conflict-of-interest issue can be seen within the Federal Drug Administration (FDA) where pharmaceutical companies pay fees for drug approval isolated from specific research projects. It is quite apparent that the FDA has come to see the pharmaceutical industry as their customer, not the American public.

Also to note: just like the pharmaceutical industry-funded studies, industry-funded cellphone studies will not release their protocols - so that there is limited assurance both as to the validity of their study procedures and the steps take to shield research from economic interests.

For example, the Interphone study protocol, a common protocol used by 13 participating countries, is kept "strictly confidential." While there is a process to maintain the independence of researchers from direct cellphone industry involvement, it is unclear as to what and how the cellphone industry was involved in the Interphone study protocol design. Certainly, the Interphone definition of "regular" cellphone use is set to such a minimal standard that few could imagine a finding of risk. Regular cellphone use is defined as cellphone use for at least once a week for six months or more, a year prior to the study cutoff date.

The important question to ask is, if this were a study of the risk of lung cancer from smoking would there be a likelihood of finding a risk of lung cancer from smokers who had smoked at least once a week for 6 months or more, a year prior to the study cutoff date? And, would there be a finding of risk, if as is the case in this study for cellphone use, the lifetime years of smoking for 10 years or more included only 3.9% of the smokers in the study?

References

[1] Affluent participating controls are more likely to use cellphone than the non-participating controls. Such a "selection bias" would result in an underestimation of the risk of glioma from cellphone use. The sheer proportion of non-participating controls makes such selection bias highly probable.

[2] Hardell et al., Environmental Research 12 July 2005 reported for wireless phone use on the same side of the head, the risk of high-grade astrocytoma was 4.2, 3.2 and 4.0 for analog and digital cellphone and cordless phone use, respectively. The Hepworth et al. paper did not reference this study, even though it was published some 4 months prior to acceptance of the Hepworth paper.

[3] Ibid, Table 5.