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Power-Line EMFs: New Focus on Alzheimer's Disease
A couple of weeks ago, a group led by Martin Röösli at Switzerland's University of Bern reported that people living within 50 meters of a high-voltage power line were more likely to die with Alzheimer's. ...
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Louis Slesin, PhD
Editor, Microwave News
A Report on Non-Ionizing Radiation
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November 17, 2008
Power-Line EMFs:
New Focus on Alzheimer's Disease
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It's not just
childhood leukemia anymore. Alzheimer's Disease is poised to take
center stage in the long-simmering EMF-health controversy.
A
couple of weeks ago, a group led by Martin
Röösli at Switzerland's University of Bern reported
that people living within 50 meters of a high-voltage power line were
more likely to die with Alzheimer's. The longer they lived near a
220-380 kV power line, the greater the risk: After 15 years, the odds
of dying with Alzheimer's were double the expected rate. It is this
striking dose-response —with the risk increasing over time—
that makes the Swiss study compelling. Röösli told
Microwave
News
that he himself found the consistency of this increase "surprising."
Other members of the Röösli team are Anke Huss, Adrian
Spoerri and Matthias Egger.
The new residential
study adds to a growing body of work that links Alzheimer's to
occupational EMF exposures. Last year, in a review for the
BioInitiative
Report,
Zoreh Davanipour and Gene Sobel concluded that there is "strong
epidemiological evidence" that magnetic fields are a risk factor
for Alzheimer's Disease. Back in 1994, Davanipour and Sobel, who are
husband and wife and are based in Chicago, were the first to make
this association (see MWN,
J/A94).
Seamstresses who use industrial sewing machines appeared to be
particularly vulnerable. "This new Swiss study strengthens my
opinion that long-term EMF exposure likely leads to Alzheimer's,"
Sobel told Microwave
News.
"I think that the association is real."
In a
meta-analysis
published in the April issue of the International
Journal of Epidemiology,
Ana Garcia of the University of Valencia, Spain, reported that the
combined data from 14 occupational studies showed that, in general,
being exposed to EMFs on the job doubled the risk of developing
Alzheimer's —about the same as Röösli found among
those exposed from power lines at home. This may well be a low
estimate, according to Sobel. If the association is real, he said,
then the true risk would be larger because Alzheimer's is often
incorrectly specified as the cause of death on death certificates. As
Röösli pointed out in his new paper, when diagnoses are
based on clinical examinations rather than on death certificates,
rates of Alzheimer's Disease can be as much two to eight times
higher.
As in all epidemiological studies, occupational or
residential, estimating exposures is at best approximate. Röösli
said that exposures above 1 µT (10 mG) from power lines are
rare in Switzerland. "I think that 0.3-0.4 µT (3-4 mG)
would be a plausible value," he said, estimating the magnetic
fields in homes next to the high-voltage lines. This is the same
level as has been implicated in studies linking childhood leukemia to
power-line EMFs.
The case favoring a link between EMFs and
Alzheimer's has only become persuasive quite recently. An earlier
meta-analysis,
published in Occupational
and Environmental Medicine
last November, found that the association was inconsistent and
unconvincing. This paper, also from Spain (Garcia worked on this one
too), appeared just five months before the Valencia study. Why the
sudden shift in outlook? The OEM
analysis only included studies published through June 2003, while the
cutoff for the IJE
paper was April 2006. During those three years four new studies came
out: three from Sweden (Feychting,
Håkansson
and Qiu)
and one from Turkey (Harmanci).
All four pointed to an Alzheimer's risk. (In an interview, Garcia
explained that her two papers appeared so close together because of
the journals' publication schedules.)
Then last year, after
Garcia's second cut-off date, two more epidemiological studies were
published: One by Röösli
and the other by Sobel
and Davanipour. Once again, both supported a link. "It is
hard to believe that these associations are entirely due to bias,"
Röösli wrote in an invited commentary
that accompanied the second Garcia meta-analysis.
Röösli
closes his new paper on residential exposures on a note of
uncertainty. "Despite the large sample size covering the whole
Swiss population, these findings must be interpreted with caution,
because of the lack of known biologic mechanisms," he wrote.
Sobel and Davanipour have tried to fill this gap: As far back as
1996, they put forward a hypothesis
that showed how EMFs could cause Alzheimer's. The process begins,
they proposed, when magnetic fields increase the flow of calcium ions
into cells. This, in turn, leads to the build-up of amyloid beta, a
known neurotoxin, in the blood stream. Amyloid beta eventually makes
its way into the brain by crossing the blood-brain barrier, where, in
ways not yet fully understood, it aggregates into plaques that are
hallmarks of Alzheimer's.
[If cell phone radiation can
increase the permeability of the blood-brain barrier —another
hot-button and unsettled issue— then it might amplify the
action of EMFs by helping amyloid beta cross from the blood stream
into the brain.]
"The new Röösli study is
consistent with our 1996 hypothesis," Sobel said, explaining
that the higher risk of Alzheimer's among those with the longest
exposure fits with the idea of accumulation of amyloid beta over
time. "It wouldn't take a lot of effort to find out whether
magnetic fields can lead to an increase of amyloid beta in the
blood," he said. In fact, Curtis
Noonan and John
Reif did measure a small increase of amyloid beta in the blood of
electric utility workers, but, as they pointed out in a paper
published in 2002, the study was limited because the workers'
exposures were quite low. "To my knowledge, this was the first
attempt to use amyloid beta as a biomarker for exposure to EMFs,"
Reif said in a telephone interview from his office at Colorado State
University. "It has yet to be replicated."
Everyone
agrees —Garcia, Röösli and Sobel— that more
work on biological mechanisms need to be done. But as Sobel points
out, "It's next to impossible to get money to do these studies."
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Copyright Microwave News 2008. All Rights Reserved.
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