We hear so much about Alzheimer's disease that
when an older person experiences memory loss or mental decline,
people may not realize that there are many other possible explanations.
That's too bad, because different underlying disorders require different
treatments and exhibit different courses over time. It might be
useful, therefore, to learn more about some common causes of mental
impairment that are not Alzheimer's disease--starting with an understanding
of the term dementia.
Understanding Dementia
Dementia is characterized by gradually progressive memory impairment,
decline in thinking ability and behavioral disturbances. The prevalence
of dementia rises with age, occurring in about 1.5% of people between
the ages of 65 and 70 but rising to 25% or more among those 85 and
older.
Dementia is not a disease, but rather a syndrome
that can be caused by many different diseases. Among the older population,
Alzheimer's disease is the commonest cause of dementia, affecting
about 4 million people and accounting for roughly six out of ten
cases. That leaves about 3 million people with dementia who suffer
from some other cause. Two of the major ones are vascular dementia
and dementia with Lewy bodies.
Vascular Dementia
Vascular dementia is usually cited as the second commonest cause
of dementia among seniors. It results from the blockage of blood
vessels, causing the destruction of brain tissue. Vascular dementia
may result from an obvious stroke or it may be due to numerous small,
unrecognized strokes. The latter scenario is called multi-infarct
dementia (an infarct is an area of tissue death due to loss of blood
flow).
The risk factors for vascular dementia are similar
to those for coronary artery disease, the disorder responsible for
angina and heart attack. Among these are high blood pressure, high
blood cholesterol, smoking and diabetes. When dementia develops
suddenly or progresses in a stepwise manner, vascular dementia is
often the culprit. However, it is often very difficult to distinguish
from Alzheimer's disease.
Dementia with Lewy Bodies
This strange-sounding disorder is unfamiliar to most Americans,
yet many authorities believe it may be even more common than vascular
dementia. Lewy bodies are the abnormal deposits within nerve cells
that give the disease its name. The deposits are also present in
the brain cells of people with Parkinson's disease.
Dementia with Lewy bodies causes memory loss,
confusion and other features of Alzheimer's, but also causes movement
disturbances resembling Parkinson's disease. These include tremor,
limb stiffness, loss of facial expression, generalized slowing of
movements and shuffling gait.
Disorders That Are Not Dementias
Some disorders that appear to cause a decline of mental function
are not dementias at all. One good example is depression. People
with depression often exhibit a slowing of mental and physical function,
loss of interest and motivation, difficulty concentrating and other
features that are easily mistaken for dementia. In fact, the term
"pseudodementia" was coined decades ago to describe this
phenomenon.
Another example is so-called mild cognitive impairment,
a condition in which memory is impaired but conclusive criteria
for dementia are lacking. Over time mild cognitive impairment can
progress to true dementia, therefore people with this disorder should
be monitored regularly.
Delirium is a syndrome of recent onset confusion,
usually accompanied by clouding of consciousness, which has superficial
resemblances to dementia. Delerium may be brought on by infections,
drug side effects, acute illnesses, metabolic disturbances and many
other provocations.
Besides these, dozens of other disorders can mimic
dementia, including certain psychiatric disorders, metabolic disturbances
and deficiencies of thyroid hormone or vitamin B12, to name just
a few.
Combinations of Disorders
To make matters even more confusing, many older individuals have
more than one problem contributing to mental decline. Mixed dementia,
for example, refers to the coexistence of Alzheimer's disease and
vascular dementia. Depression can accompany dementia of any cause;
in fact, depression is always a risk when an individual suffers
from any chronic, debilitating disease.
Another common scenario is the development of
delirium in someone with existing dementia. Hospitalization or illness
can trigger this phenomenon, in which a person with relatively mild
dementia becomes suddenly more confused or agitated.
What to Do?
Too many people, some health professional included, have a defeatist
attitude about dementia and related disorders. That's a shame, because
only by thorough investigation can an accurate diagnosis be made.
Knowing the diagnosis in turn allows for proper treatment selection--and
also for the avoidance of inappropriate or ineffectual treatments.
Just as important, a diagnosis empowers patients and families to
cope better today and plan more knowledgably for tomorrow.
Where to Get Additional Information:
The Alzheimer's Disease Education and Referral Center (ADEARS) is
an excellent service of the National Institute on Aging offering
information about many other disorders in addition to Alzheimer's.
(800) 438-4380 www.alzheimers.org
August, 2003 |
