Recent study claims no evidence of a link between cellphone use and cancer but results were contradictory, leading in both directions
Recently, the British Medical Journal published a paper
evaluating the relationship between mobile phone use and gliomas, a
type of a cancer that represents 50% of all primary brain tumors. The
researchers found no evidence to support the claim that cell phone use
increases the likelihood of being diagnosed with a glioma.
Unfortunately this doesn't mean that we know cell phones are safe.
In
this case-control study, the researchers interviewed 966 patients who
had been diagnosed with a glioma in the UK. These patients were asked
to recall the frequency and duration of their calls, the side of their
head that the phone was used on, whether or not they used hands-free
ear pieces, as well as the specific types of phones that were used. The
researchers then obtained the same information from 1,716 individuals
who did not have cancer. When the two groups were compared, no evidence
was found to suggest that there was an increased risk of glioma
compared to the cumulative number of calls and hours of use.
The
researchers did however encounter interesting findings. There was
evidence suggesting that there was a higher risk of developing a tumor
on the same side of the brain where the phone was used. Their 95%
confidence interval was 1.02 to 1.52, meaning that there was somewhere
between 2 to 52% increase in risk for developing a tumor and that there
was only a 5% chance that the difference could be less than 2% or
higher than 52%. In parallel to this finding, they found a reduced risk
of tumor when the phone was used on the opposite side of the head. This
time, the range was a 7 to 39% reduction in risk with only a 5% chance
that the reduction in risk was less than 7% or greater than 39%.
Despite
their conclusion about having no evidence, this bit of data actually
supports the claim that cell phones can be dangerous. However, the
researchers write that these differences are due to recall bias because
patients know the side of their brain that has cancer. Patients may be
biased into reporting that they used the cell phone more frequently on
the cancerous side.
This inadequate evidence for either
conclusion captures the problem of a case-control study: recall bias.
If you cannot trust your subjects to accurately remember which side of
their heads they use their phones on more frequently, how can you trust
the rest of the data? Other problems with the study were that the
researchers were only able to interview 51% of the patients who they
identified as having gliomas "mainly because rapid death prevented [the
researchers] from approaching all of them." Finally, the researchers
only looked at one type of brain tumor and not others.
In the
end, the study does not give any definitive results. It simply says
that evidence could not be found on whether or not cellphones were
dangerous. In addition, there was statistical evidence
suggesting that tumors were more likely to be seen on the same side a
phone was used, although there are confounding variables that may come
into play.
While a cohort study (where people are followed
over time) would be better than the case-control study (where people
are asked to look back in time), the nature of medical research
involves doing lower-budget research first before moving on. These
types of studies open the door for more expensive and bigger studies.
Bottom line? More research is needed before we really know the answer.
More information on gliomas can be found here.
Original article: Hepworth SJ, et. al. Mobile
phone use and risk of glioma in adults: case-control study. BMJ,
doi:10.1136/bmj.38720.687975.55 (published 20 January 2006)
"If you look at the last five years, if you look at what major innovations have occurred in computing technology, every single one of them came from AMD. Not a single innovation came from Intel." -- AMD CEO Hector Ruiz in 2007
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