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Chatting On Your Cell Phone
May Boost Brain Metabolism
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November 4, 2011 | By John Timmer
The concerns about the health impacts of cellphone use are
likely to resurface today with the publication of a study in
JAMA, the Journal of the American Medical Association.The
study doesn’t uncover any health risks associated with
cellphone use, but it does indicate that holding a phone to
one’s head for an extended call seems to be enough to boost
the brain’s metabolic rate. The boost, however, is smaller
than that seen in the visual system when it’s processing
images.
The new report comes against a backdrop of persistent fears
about possible health risks associated with heavy cellphone
use. Different studies that have tested for associations
between heavy usage and cancer have generally produced
negative results, although there are some notable
exceptions, and cell phones haven’t been around long enough
for there to be good measures of risk associated with
multi-decade use. Even if the epidemiological data has
remained slightly ambiguous, however, the biology hasn’t:
there’s no known mechanism that could lead from low-energy,
long-wavelength radiation to cancer.
That doesn’t mean that cell phones do nothing; radiation in
these frequencies is likely to heat nearby tissues. A few
other biological effects have been proposed but, so far at
least, they haven’t been seen consistently. (The authors
cite some of these other findings, assigning them a bit too
much credibility, in my judgement).
The new study attempts to show there’s more going on than
simply heating by tying cell phone use to changes in the
brain’s metabolism. Even here, however, past experiments
have caused a bit of confusion. Studies based on tracking
blood flow or metabolic activity in the brain have found
just about any result imaginable, from increases near the
site of the cell phone to decreases there and increases
elsewhere in the brain. It’s difficult to make any sense of
them at all.
To get around some of these problems, the authors simply
recruited nearly 50 participants; previous studies they cite
typically involved 20 people or less. For measuring
metabolic activity, they went with the PET scan. PET
involves giving the subject a form of the sugar glucose, in
which one of the atoms is radioactive. Its decay emits a
small bit of antimatter—a positron—that in turn emits a
gamma ray when it collides with a regular electron. By
figuring out where the gamma rays are coming from, we can
tell where the glucose is going, and thus which cells are
most active. PET provides a picture of metabolic activity
that covers a longer time period than the transient
responses seen with blood flow imaging.
(Appreciate, for the moment, the idea of looking into
potential health implications of weak cellular radiation by
triggering matter-antimatter annihilations inside the
brain.)
You should also appreciate the experimental procedure. To
blind the participants, the authors strapped two cell phones
on their heads, one to each ear (the cellphone used in this
work is a standard Samsung CDMA flip phone). Both were kept
muted, and only one was activated by a call—the side that
was activated was flipped in two different recording
sessions. The calls started 20 minutes before a dose of
radioactive glucose, and kept going for a half an hour
afterwards to provide a long-term picture of metabolic
activity. The data from one of the subjects ended up not
being used because the cell company dropped the call.
After recording the results, the authors looked for
differences across the experimental and control tests. To
simplify the calculations, however, they narrowed their
focus to regions that are likely to be exposed to
substantial amounts of radiation from the cell phone’s
antenna—only areas projected to receive 50 percent or more
of the maximum power were compared. This might explain why
the results were a bit less confused than earlier work, but
it could also mean that areas of the brain that could
produce confusing results were ignored.
In any case, on a whole-brain level, there wasn’t any
significant difference between having an active cell phone
strapped to your head and having an unused one. But, when
individual areas are compared, some differences do leap out:
the signal increased in the areas that received the
strongest cellular signal. Since the antenna was in the base
of the handset, this meant that the bottom-front of the
brain lit up.
What does this mean? It’s not entirely clear. Typically,
these signals increase in response to enhanced activity in
the neurons there, and the authors propose that the same is
true here, meaning that localized exposure to a cell phone
causes the neurons there to fire more often. But that has
not been demonstrated by this work, and there’s still no
obvious mechanism by which it would occur.
Does it represent a health risk? The authors have no idea,
and say as much. However, they also note that the increase
in activity seen here is actually less dramatic than that
seen when the brain goes to work on a visual task. And there
has been no indication that excessive mental activity causes
health problems; in fact, the exact opposite appears to be
the case.
Mauritania, Nouakchott,
The Hague, Netherlands
Lithuania, Vilnius,
Madagascar, Antananarivo,
Henderson, Nevada
Tamworth, Australia
Lithuania, Vilnius
Birmingham, Alabama
Berkeley, California
Kawr Fakkan, United Arab Emirates, Kawr Fakkan, UAE
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