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Alzheimer's disease
Current trends and future advances
in therapeutic management
BY Serge Gauthier, MD
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When considering our aging population and
the public's awareness of the availability of treatments, it's very
likely that the prevalence of Alzheimer's disease will increase
in the coming years. Moreover, individuals concerned about their
own genetic risks are motivated into getting older relatives properly
diagnosed early on. New population-based figures will be required,
however, to compare with data collected during the Canadian Study
of Health and Aging in 1991, which was the first country-wide prevalence
study for Alzheimer's disease and vascular dementia — 8% of
people over age 65 had one or the other. The big revelation was
that 16.8% of individuals over age 65 were cognitively impaired
without reaching the threshold for dementia. A follow-up study five
years later showed an incidence of 21.8 for women and 19.1 for men
per 1,000 non-demented persons per year (60,150 new cases of dementia,
the majority being from Alzheimer's disease, per year). There's
hope that control of vascular risk factors, such as arterial hypertension
in mid-life (age 40-60 years), combined with higher education levels
and better diet (i.e. fish and red wine) will decrease the incidence
of Alzheimer's disease in one generation.
Does
an early diagnosis matter?
Earlier diagnosis of Alzheimer's disease is possible through
higher sensitivity of physicians to memory complaints, particularly
if brought up by family members or friends. The Mini-Mental State
Examination (MMSE) and the Montreal Cognitive Assessment (MoCA,
available through www.mocatest.org)
allow for measurement of cognitive changes over time, and are increasingly
considered the best screening tests for persons with cognitive complaints.
Direct observations by occupational therapists may further be required
to assess executive abilities and functional autonomy at home —
and behind the wheel of a car!
There are currently no biologic tests (i.e.
blood work, cerebrospinal fluid or brain scans) specific enough
for detection of Alzheimer's disease that can be used in daily clinical
practice. It's possible, however, that a combination of cerebrospinal
fluid markers such as amyloid-beta 42 protein (Aβ42) and tau
(a protein found in brain plaques), along with brain positron emission
tomography for glucose or amyloid, will make it possible to establish
a very early diagnosis — perhaps before any symptoms begin
to manifest.
There is ongoing debate, though, as to whether
mild cognitive impairment can be considered a diagnosis of very
early Alzheimer's or a syndrome of memory complaints (usually subjective),
but which doesn't impact on daily life, is often reversible, and
has multiple etiologies (i.e. depression, hypothyroidism, substance
abuse or sleep apnea). A prudent approach is to rule out systemic
and psychiatric causes of mild cognitive impairment, and to reassess
the patient at least once a year for the possibility of "conversion"
to early dementia, one of the clinical milestones of Alzheimer's
disease (see
Table 1).
Once mild dementia of the Alzheimer's disease
type has been diagnosed, a number of issues need to be dealt with.
For one, explain the diagnosis to the patient and family, taking
into account the risk of depression, and educate them about the
natural history of the disease. Advise them to keep legal documents
updated, such as a will, power of attorney and a mandate (in case
of incapacity). Encourage patients and their families to join support
groups through local Alzheimer's disease societies or other community
resources. Pharmacotherapy, such as antidepressants (when required)
and cholinesterase inhibitors can be offered. Retirement issues
will need to be worked out for individuals who are still working
and in addition, these patients' ability to drive should be monitored
regularly.
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