Sometimes the situation with Alzheimer's
feels like a runaway train. You can't fix the brakes
but you can always polish the windscreen to get
a better view of the oncoming disaster.
Alzheimer's cases are set to quadruple
over the next 40 years and there's still not much available
by way of treatment. Research presented at the Alzheimer's
Association Conference (AAC) in Washington, DC, earlier
this month showed again that all of the successful research
at the moment is concentrated in the field of diagnosis.
DIRE
STRAITS
Researchers from Johns Hopkins University predict that
106 million people will have Alzheimer's by 2050. The
study was presented at the AAC and appears in the July
issue of Alzheimer's and Dementia. More than
26 million people worldwide have Alzheimer's disease
today, with Asia being home to nearly half the world's
cases.
"If we can make even modest advances
in preventing Alzheimer's disease, or delay its progression,
we could have a huge global public health impact," said
lead researcher Ron Brookmeyer, PhD. Delaying average
onset of disease by just one year would cut the number
of cases in 2050 by 12 million, according to the study.
While the figures are alarming,
it's worth noting that the predicted global burden of
Alzheimer's disease in 2050 one case per 85 people
is hardly any higher than the current burden
in Canada. With its relatively aged population, Canada
already has 280,000 full-blown cases of Alzheimer's,
and this is expected to rise to a terrifying 750,000
by 2050.
CRYSTAL
BALL
It's small consolation, but at least we'll be very good
at anticipating these tragedies by then. The diagnosis
and prediction of Alzheimer's and milder forms of cognitive
impairment is advancing by leaps and bounds.
Three new techniques were unveiled
at the AAC. In one, researchers from University of Pennsylvania
and the National Institute on Aging combined and analysed
MRI images measuring the density and volume of various
different tissues and their spatial distribution within
the brain. Using a complex algorithm, they were able
to distinguish patients diagnosed with mild cognitive
impairment from healthy controls with 100% accuracy.
"Our study is the first to show
that using MRI techniques to classify tissue patterns
in the brain provides very high diagnostic accuracy
on an individual basis," said Dr Cristos Davatzikos,
of Penn State. Unfortunately it does so at the cost
of several thousand dollars per patient.
Perhaps of more immediate application
is a "bedside algorithm" developed by Dr Deborah Barnes
of the University of California, San Francisco, which
effectively sorts patients' dementia risk into low,
medium and high risk categories. Six percent of her
low risk group will progress to Alzheimer's, she said,
compared to 54% of the high risk group. It's good enough
to provide reassurance to the low risk group, and may
motivate those at high risk to modify their lifestyles,
she argues.
A third diagnostic tool was presented
by a private Norwegian company, DiaGenic ASA. Using
a 1,200-gene DNA micro-array, this method achieved 85%
specificity in distinguishing Alzheimer's patients from
healthy subjects. But these were patients with advanced
disease whom any clinician could have diagnosed from
their symptoms. Whether the test will predict earlier-stage
disease remains to be seen.
SEARCH
FOR ANSWERS
There is sadly not much to be done with these diagnoses
in the absence of better treatments. The four drugs
currently approved for Alzheimer's donepezil,
memantine, galantamine and rivastigmine tartrate
have achieved modest delays in progression at best,
and the drug pipeline is not looking like it contains
any sort of radical breakthrough.
At the AAC, it was all about managing
expectations on the treatment side of the equation.
"I think this is just exactly what we should expect
incremental progress," Dr Sam Gandy, chairman
of the Alzheimer's Association's medical and science
council, told reporters. He predicted that in the near
future, patients are likely to receive a cocktail of
drugs, since none stands out from the crowd.
The two drugs closest to market
show signs of promise, but any improvement over the
current generation is likely to be incremental. A compound
called AC-1202 slows disease progression over nine months,
at least in patients without the Alzheimer's gene APOE-4.
Another compound called LY450139
that interferes in the formation of amyloid protein
was found to reduce this building-block of Alzheimer's
plaques by up to 65% in some subjects. But its clinical
effects have yet to be measured. The drug has already
passed safety tests, though not without revealing some
odd side effects, including a tendency to lighten hair
colour.
JAB
IN THE WORKS
The June 29 issue of the Journal of Biological Chemistry
reports on the development of an Alzheimer's "vaccine"
based on antibodies to amyloid precursor protein. Wyeth
and Irish partner Elan have a vaccine under development,
but it hit a major snag in early trials when 6 % of
subjects developed encephalitis. The problem is being
studied.
The most reliable way we have of
avoiding dementia, it seems, is to keep our brains active.
This is confirmed yet again in a study in the June 27
issue of Neurology. A longitudinal study of more
than 1,200 older people 90% of whom went on to
develop Alzheimer's found that a cognitively
active person in old age was 2.6 times less likely to
develop dementia and Alzheimer's disease than a cognitively
inactive person.
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