If heart disease and diabetes aren't bad
enough, now comes another reason to watch your weight.
According to a study just released, packing on too many
pounds can increase the risk of developing Alzheimer's
disease.
A team led by researchers at the Farber Institute for
Neurosciences at Thomas Jefferson University in Philadelphia
and Edith Cowan University in Joondalup, Western Australia
has shown that being extremely overweight or obese increases
the likelihood of developing Alzheimer's. They found a
strong correlation between body mass index and high levels
of beta-amyloid, the sticky protein substance that builds
up in the Alzheimer's brain and is thought to play a major
role in destroying nerve cells and in cognitive and behavioral
problems associated with the disease.
"We looked at the levels of beta-amyloid and found
a relationship between obesity and circulating amyloid,"
says Sam E. Gandy, M.D., Ph.D., director of the Farber
Institute for Neurosciences.
"That's almost certainly why the risk for Alzheimer's
is increased," says Dr. Gandy, who is also professor
of neurology, and biochemistry and molecular biology at
Jefferson Medical College of Thomas Jefferson University.
"Heightened levels of amyloid in the blood vessels
and the brain indicate the start of the Alzheimer's process."
The scientists reported their findings this month in the
Journal of Alzheimer's Disease.
According to, Dr. Gandy, evidence has emerged over the
last five years that many of the conditions that raise
the risk for heart disease such as obesity, uncontrolled
diabetes, hypertension and hypercholesterolemia also increase
the risk for Alzheimer's. Yet exactly how such factors
made an individual more likely to develop Alzheimer's
remained a mystery.
Dr. Gandy, Ralph Martins, Ph.D., of Edith Cowan University
and their colleagues measured body mass index and beta-amyloid
levels in the blood. They also looked at several other
factors associated with heart disease and diabetes, such
as the inflammatory marker C-reactive protein, insulin,
and high density lipoprotein in 18 healthy adults who
were either extremely overweight or obese. They found
a "statistically significant correlation" between
body mass index and beta-amyloid.
"Ours is one of the first attempts to try to find
out on both the pathological and the molecular levels
how obesity was increasing the risk of Alzheimer's,"
says Dr. Gandy, who serves as chairman of the Alzheimer's
Association's Medical and Scientific Advisory Council.
One implication of these findings could be that by losing
excess weight and maintaining normal body weight, an individual
might reduce the risk of developing Alzheimer's. However,
this has not been proven, notes Dr. Gandy.
"What's especially interesting about this is that
several studies are showing that even medical conditions
in midlife may predispose to Alzheimer's later on,"
he says. "The baby boomers today should pay attention
to this. Their medical risk factors today will play a
role 30 years later. Think about weight, cholesterol,
blood pressure, which could affect you long-term. In terms
of Alzheimer's, another risk factor is maintaining an
active mental lifestyle."
The next step is to follow such patients over the long
term to see how many do indeed develop Alzheimer's. "We
need to first develop a medicine that is effective in
humans in lowering amyloid accumulation or generation,"
says Dr. Gandy. "We have those now in mice and we
are testing them in humans. If we can develop such a medicine,
then the question will be, if we can lower amyloid, will
that in fact prevent Alzheimer's?"
