Alternate Names : Organic Brain Syndrome
Alzheimer's disease is a common, progressive, degenerative disease
of the brain. It is characterized by loss of
memory and other cognitive functions. Among people aged 65 or older, it
is the most common cause of dementia.
Dementia is a group of symptoms marked by the gradual loss of mental
What is going on in the body?
People who have Alzheimer's disease have abnormal deposits of a protein called
beta-amyloid. Abnormal structures called plaque are formed from a combination
of destroyed nerve cells and the beta-amyloid. Tangles of nerve fibers are
formed from abnormal nerve cells along with a type of protein called TAU. As
the tangles and plaque develop, nerve cell connections are reduced. The
elimination of nerve cell connections causes damage to certain pathways in the
brain. These pathways are essential for thinking, learning, and memory.
People who have Alzheimer's disease have smaller brains than the normal population. They also
have lower amounts of a neurotransmitter called acetylcholine. This chemical is
essential for memory and thinking.
What are the causes and risks of the disease?
The cause of Alzheimer's disease is unknown. Factors that may increase the risk
of developing Alzheimer's disease include the following:
genetics. Scientists have found links between the disease and certain
chromosomes, including chromosomes 10, 14, 19, and 21. Individuals with Down syndrome, an abnormality of
the 21st chromosome, have a significantly higher risk of developing Alzheimer's
age. Most people with Alzheimer's disease are older than age 65, although
it is sometimes seen in individuals in their 30s, 40s, and 50s. Alzheimer's
disease is seen in 1 out of 4 people over the age of 85.
educational level or cognitive activities, which are tasks that involve
active learning in the brain. Several research studies have shown that
Alzheimer's disease is less likely to develop in individuals who have reached
higher educational levels or have jobs that are more intellectually stimulating.
Cognitive activities such as reading are associated with a later onset of
estrogen. There is some research suggesting a possible link between the
hormone estrogen and Alzheimer's
disease in women. Menopause, the stage of life when a woman stops
having periods and her body makes little estrogen, is associated with an
increase in the onset of Alzheimer's disease.
head injuries. A recent study
of US armed forces veterans showed that a head injury early in life is associated with a
higher risk of Alzheimer's disease and other forms of dementia as the veterans aged. Furthermore, the risk of
Alzheimer's disease increased with the severity of the head injury in early
environmental toxins, such as aluminum and mercury. There has been
conflicting research about the accumulation of heavy metals in the brains of
individuals with Alzheimer's disease.
chemical deficiencies. People with Alzheimer's disease have a lower than
normal level of acetylcholine in their brains.
autoimmune disorder, which is a condition in which the body attacks its own
cells. Some researchers have found antibrain antibodies in the brains of people
with Alzheimer's disease.