A new study throws light on many hidden corners of the rapidly degenerating mind
ALZHEIMER disease (AD) is now recognised as a serious public health problem.
in a large number of people, AD develops at a rather late age of about 65
years. Alzheimer was hitherto considered to be a Western problem
because of longer life span - the us for
example has over four million people
with this degenerative brain disorder.
But of late, AD is rapidly emerging as a
important problem for the Indian senior citizens.
The Journal of American Medical
Association (JAMA) has just
brought out a special issue on
Alzheimer disease, highlighting advancements made this
year. Among the significant
results is the relationship
between strokes and AD by
David Snowdon and his colleagues from the University
of Kentucky, Lexington.
Snowdon's group was looking for clues to understand
ageing and they persuaded
members of a Roman Catholic religious order, the
School Sisters of Notre Dame
in Mankato, Minnesota, to
participate in this study. The
sisters took regular psychological tests and gave regular
blood samples. He also made
an unusual request: would
they be willing to donate their brains
after death? 678 nuns who were 75 or
over signed up and so the study took off
(JAMA, Vol 277, No 10).
The investigators V the break-
through when Sister Mary died in 1995,
at the age of I0I and her brain was
examined. Researchers saw in her brain
signs of devastation from microscopic
plaques and tangles to gaping holes
where millions of brain cells had died
although she was quite normal and
active until her death. Slowly
Snowdon's group realised that Sister
Mary was not unique. Until then they
had considered these old ladies as a
model of successful ageing as despite
advanced age most of them could live a
near normal life both in respect of intellectual and physical functions. There
were 19 among the 61 deceased nuns
who seemed to have escaped the confusion and memory loss that makes this
form of dementia (irreversible organic
deterioration of mental faculties) so devastating.
According to them the reason
appears to be that these nuns, unlike
their counter parts whose symptoms
were severe, had not suffered from
strokes, especially small strokes so commonplace in the elderly. They noticed
that only 57 per cent of the stroke-free
nuns developed dementia as compared
to over 93 per cent of nuns with a history
of mini-strokes. This is considered an
important finding, since it provides
what may be the clearest sign yet that a
medically treatable condition like stroke
can accelerate the decline of Alzheimer's
patients and makes the difference
between independent living and nursed
at home. By preventing strokes in
older people, it may now be possible to
postpone the development of symptoms
of people with AD.
Even if medical researchers can
use this information to be able to
reduce the symptoms of people with AD,
they would have achieved a greater
deal. Besides costing a lot to the health
care systems and patients' families,
the social consequences of nursing a
parent with AD are significant. Scientists
estimate that postponing the symptoms of AD by five years could cut the
health care costs by nearly half and the
patient will have five more years of near normal life.
Scientists have been looking for
clues to understand what causes
Alzheimer's and what we have now
are a intriguing set of hypothesis.
The most popular theory holds that the
disease process starts when a protein
called beta amyloid accumulates outside
the nerve cells, forming the deposits
known as plaques. The plaques
appear to impair the ability of the
neurons in the brain to absorb
glucose from the blood stream resulting
in the devastating mental problems.
Another hypothesis says that AD begins
not with beta amyloid but with a
protein called tau. According to the
proponents of this theory, abnormal
variants of this protein clutter the
interiors of the neurons with tangled
filaments that disrupt cellular metabolism.
Researchers have now
realised through the study of
genes that contribute to the
formation of these lesions
that both theories may be
true. People with this defective gene involved in making
beta amyloid have high rates of AD. But there are
others with a AD-susceptibility
gene called Apo-E4, which produces a protein that appears to affect tau. According to AD researchers,
people who carry two copies
of this gene have an elevated
risk of developing AD before
70. And if they suffer a stroke,
they are more likely to develop
full-blown dementia.
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