Abuja - Swedes who talked on mobile or
cordless phones for more than 25 years had
triple the risk of a certain kind of brain cancer
compared to those who used wireless phones
for less than a year, a new study suggests.
The odds of developing glioma, an often
deadly brain cancer, rose with years and
hours of use, researchers reported in the
journal Pathophysiology.
"The risk is three times higher after 25 years
of use. We can see this clearly," lead
researcher Dr. Lennart Hardell told Reuters
Health in a telephone interview.
His finding contrasts with the largest-ever
study on the topic – the international
Interphone study, which was conducted by the
International Agency for Research on Cancer
and funded in part by cell phone companies.
That study, published in 2010, failed to find
strong evidence that mobile phones increased
the risk of brain tumours.
Even if the odds of developing a glioma were
doubled or tripled, however, the risk would
still remain low.
Brain tumours and phone use
A little more than 5 out of 100 000 Europeans
(or 0.005 percent) were diagnosed with any
kind of malignant brain tumour between 1995
and 2002, according to a 2012 study in the
European Journal of Cancer. If the rate triples,
the odds rise to about 16 out of 100,000 (or
0.016 percent).
Hardell, an oncologist from University Hospital
in Orebro, Sweden, and his colleague Michael
Carlberg matched 1 380 patients with
malignant brain tumours to people without
such tumours and compared their wireless
phone use.
People who reported using wireless phones for
20 to 25 years were nearly twice as likely to
be diagnosed with glioma as those who
reported using them for less than a year, the
study found. Those who used cell and cordless
phones for more than 25 years were three
times more likely to develop one of these
tumours.
The study did not show an association of
wireless phones with malignant brain tumours
other than glioma.
Participants who recalled talking the most –
more than 1,486 hours – on wireless phones
were twice as likely to develop glioma
compared to those who said they used the
devices the fewest hours – between one and
122 hours, the study found.
Case control studies such as this suffer from a
number of limitations, however, the most
serious being the need for participants to
remember their behaviour patterns from
decades earlier.
Take precaution
Dr. Gabriel Zada, a neurosurgeon at the
University of Southern California's Keck School
of Medicine, who wasn't involved in Hardell's
study, advises precautionary measures, such
as using the phone's speaker or a hands-free
headset.
But he told Reuters Health the new study
failed to answer his patients' questions about
why they developed brain tumours.
"A lot of people ask me, 'Why did I get this
brain tumour?'" he said. "There are a lot of
different theories. It's a much more
convoluted picture than just saying cell phones
caused this."
In a 2012 study, Zada reported that rates of
malignant tumours in parts of the brain
closest to where people hold their phones rose
significantly in California from 1992 to 2006 –
although the incidence of gliomas throughout
the brain decreased.
U.S. cell phone use tripled between 2000 and
2010, according to CTIA - the Wireless
Association, which represents manufacturers.
But in the U.S. overall, rates of cancer in parts
of the brain that would be more highly
exposed to radiofrequency radiation from cell
phones had not gone up at the time of a 2010
report in the journal Neuro-Oncology.
Zada believes the current study underscores
the need for more research.
"It is more evidence suggesting a possible
association between brain tumours and cell
phones," he said. "But it's certainly not
convincing that cell phones cause brain
cancer."
Mobile phones carcinogenic?
A World Health Organisation panel of 31
scientists from 14 countries classified mobile
phones as "possibly carcinogenic" in 2011. The
U.S. Federal Communications Commission is
currently reassessing the safe radiation
exposure limits it adopted in 1996.
Cell phones emit radiofrequency energy, which
can be absorbed by tissues closest to where
the phone is held, the National Cancer
Institute says on its website. "Studies thus far
have not shown a consistent link between cell
phone use and cancers of the brain, nerves,
or other tissues of the head or neck," it says.
Hardell is one of the few researchers who
include cordless phones when studying cell
phones and cancer risk. He believes emissions
from the base stations of cordless phones can
be problematic, especially when users sleep
next to them.
Children may be most vulnerable to wireless
phone emissions, Hardell said. They absorb
more radiofrequency electromagnetic fields, he
writes, because of their small heads, thinner
skulls and higher brain conductivity.
"Girls tends to put the smart phone below the
pillow," he said. "It's a bad habit to go to bed
with your smart phone."
Zada also believes developing brains may be
more susceptible and recommends against
sleeping with cell phones.
Nevertheless, he said: "It's hard to make
formal recommendations because the data is
lacking. It's not smoking and lung cancer
because it's not proven.
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