What is dementia?
Dementia is the loss of mental functions—such as thinking, memory, and
reasoning—that is severe enough to interfere with a person’s daily
functioning. Dementia is not a disease itself, but rather a group of symptoms
that might accompany certain diseases or conditions. Symptoms also might include
changes in personality, mood, and behavior. Dementia is irreversible when caused
by disease or injury, but might be reversible when caused by drugs, alcohol,
hormone or vitamin imbalances, or depression.
Dementia develops when the parts of the brain that are involved with
learning, memory, decision-making, and language are affected by any of various
infections or diseases. The most common cause of dementia is Alzheimer’s
disease, but there are as many as 50 other known causes. Most of these causes
are very rare.
Some of the disorders that cause dementia might be reversible, although
unfortunately most types of dementia do not respond to treatment. Therefore, it
is very important to evaluate dementia symptoms comprehensively, so as not to
miss potentially treatable conditions. The frequency of "treatable"
causes of dementia is believed to be about 20 percent.
What are some of the other causes of dementia?
There are many causes of dementia, including neurological disorders such as
Alzheimer's disease, blood flow-related (vascular) disorders such as
multi-infarct disease, inherited disorders such as Huntington's disease, and
infections such as HIV. The most common causes of dementia include:
- Degenerative neurological diseases, such as Alzheimer's, dementia with
Lewy bodies, Parkinson's, and Huntington's
- Vascular disorders, such as multiple-infarct dementia, which is
causes by multiple strokes in the brain
- Infections that affect the central nervous system, such as HIV
dementia complex and Creutzfeldt-Jakob disease
- Chronic drug use
- Depression
- Certain types of hydrocephalus, an accumulation of fluid in the
brain that can result from developmental abnormalities, infections, injury, or
brain tumors
Alzheimer's disease causes 50 percent to 70 percent of all dementia. However,
researchers are finding that some of what was previously considered Alzheimer's
disease is really one of two other degenerative diseases: Lewy body disease and
Pick's disease. There also are a number of other important disorders that can
lead to dementia. Some of these are potentially reversible, at least partially,
and should be considered before a diagnosis of Alzheimer's disease is made.
How common is dementia?
Although dementia has always been somewhat common, it has become even more
common among the elderly in recent history. It is not clear if this increased
frequency of dementia reflects a greater awareness of the symptoms, or if people
simply are living longer and thus are more likely to develop dementia in their
older age.