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A woman in her early 50s was admitted to a hospital because
of increasingly odd behavior. Her family reported that she had been
showing memory problems and strong feelings of jealousy. She also
had become disoriented at home and was hiding objects. During a
doctor's examination, the woman was unable to remember her husband's
name, the year, or how long she had been at the hospital. She could
read but did not seem to understand what she read, and she stressed
the words in an unusual way. She sometimes became agitated and
seemed to have hallucinations and irrational fears.
This woman, known as Auguste D., was the first person reported to have the
disease now known as Alzheimer's disease * (AD) after
Alois Alzheimer, the German doctor who first described it. After Auguste D.
died in 1906, doctors examined her brain and found that it appeared shrunken
and contained several unusual features, including strange clumps of protein
called plaques and tangled fibers inside the nerve cells. Memory
impairments and other symptoms of dementia, which means "deprived
of mind," had been described in older adults since ancient times. However,
because Auguste D. began to show symptoms at a relatively early age, doctors
did not think her disease could be related to what was then called "senile
dementia. "The word senile is derived from a Latin term that means, roughly,
It is now clear that AD is a major cause of dementia in elderly
people as well as in relatively young adults. Furthermore, we know
that it is only one of many disorders that can lead to dementia. The
U. S. Congress Office of Technology Assessment estimates that as
many as 6.8 million Americans have dementia, and at least 1.8
million of those are severely affected. Studies in some communities
have found that almost half of all people age 85 and older have some
form of dementia. Although it is common in very elderly individuals,
dementia is not a normal part of the aging process. Many people live
into their 90s and even 100s without any symptoms of dementia.
Besides senile dementia, other terms often used to describe
dementia include senility and organic brain syndrome.
Senility and senile dementia are outdated terms that reflect the
formerly widespread belief that dementia was a normal part of aging.
Organic brain syndrome is a general term that refers to physical
disorders (not psychiatric in origin) that impair mental
Research in the last 30 years has led to a greatly improved
understanding of what dementia is, who gets it, and how it develops
and affects the brain. This work is beginning to pay off with better
diagnostic techniques, improved treatments, and even potential ways
of preventing these diseases.
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Dementia is not a specific disease. It is a descriptive term for
a collection of symptoms that can be caused by a number of disorders
that affect the brain. People with dementia have significantly
impaired intellectual functioning that interferes with normal
activities and relationships. They also lose their ability to solve
problems and maintain emotional control, and they may experience
personality changes and behavioral problems, such as agitation,
delusions, and hallucinations. While memory loss is a common symptom
of dementia, memory loss by itself does not mean that a person has
dementia. Doctors diagnose dementia only if two or more brain
functions - such as memory, language skills, perception, or
cognitive skills including reasoning and judgment - are
significantly impaired without loss of consciousness.
There are many disorders that can cause dementia. Some, such as
AD, lead to a progressive loss of mental functions. But other types
of dementia can be halted or reversed with appropriate
With AD and many other types of dementia, disease processes cause
many nerve cells to stop functioning, lose connections with other
neurons, and die. In contrast, normal aging does not result in the
loss of large numbers of neurons in the brain.
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Dementing disorders can be classified many different ways. These classification
schemes attempt to group disorders that have particular features in common,
such as whether they are progressive or what parts of the brain are affected.
Some frequently used classifications include the following:
- Cortical dementia - dementia where the brain
damage primarily affects the brain's cortex, or outer layer. Cortical dementias
tend to cause problems with memory, language, thinking, and social behavior.
- Subcortical dementia - dementia that affects
parts of the brain below the cortex. Subcortical dementia tends to cause
changes in emotions and movement in addition to problems with memory.
- Progressive dementia - dementia that gets worse
over time, gradually interfering with more and more cognitive abilities.
- Primary dementia - dementia such as AD that
does not result from any other disease.
- Secondary dementia - dementia that occurs as
a result of a physical disease or injury.
Some types of dementia fit into more than one of these
classifications. For example, AD is considered both a progressive
and a cortical dementia.
Alzheimer's disease is the most common cause of
dementia in people aged 65 and older. Experts believe that up to 4
million people in the United States are currently living with the
disease: one in ten people over the age of 65 and nearly half of
those over 85 have AD. At least 360,000 Americans are diagnosed with
AD each year and about 50,000 are reported to die from it.
In most people, symptoms of AD appear after age 60. However,
there are some early-onset forms of the disease, usually linked to a
specific gene defect, which may appear as early as age 30. AD
usually causes a gradual decline in cognitive abilities, usually
during a span of 7 to 10 years. Nearly all brain functions,
including memory, movement, language, judgment, behavior, and
abstract thinking, are eventually affected.
AD is characterized by two abnormalities in the brain:
amyloid plaques and neurofibrillary tangles.
Amyloid plaques, which are found in the tissue between the nerve
cells, are unusual clumps of a protein called beta amyloid
along with degenerating bits of neurons and other cells.
Neurofibrillary tangles are bundles of twisted filaments found
within neurons. These tangles are largely made up of a protein
called tau. In healthy neurons, the tau protein
helps the functioning of microtubules, which are part of the cell's
structural support and deliver substances throughout the nerve cell.
However, in AD, tau is changed in a way that causes it to
twist into pairs of helical filaments that collect into tangles.
When this happens, the microtubules cannot function correctly and
they disintegrate. This collapse of the neuron's transport system
may impair communication between nerve cells and cause them to
Researchers do not know if amyloid plaques and neurofibrillary
tangles are harmful or if they are merely side effects of the
disease process that damages neurons and leads to the symptoms of
AD. They do know that plaques and tangles usually increase in the
brain as AD progresses.
In the early stages of AD, patients may experience memory
impairment, lapses of judgment, and subtle changes in personality.
As the disorder progresses, memory and language problems worsen and
patients begin to have difficulty performing activities of daily
living, such as balancing a checkbook or remembering to take
medications. They also may have visuospatial problems, such as
difficulty navigating an unfamiliar route. They may become
disoriented about places and times, may suffer delusions (such as
the idea that someone is stealing from them or that their spouse is
being unfaithful), and may become short-tempered and hostile. During
the late stages of the disease, patients begin to lose the ability
to control motor functions. They may have difficulty swallowing and
lose bowel and bladder control. They eventually lose the ability to
recognize family members and to speak. As AD progresses, it begins
to affect the person's emotions and behavior. Most people with AD
eventually develop symptoms such as aggression, agitation,
depression, sleeplessness, or delusions.
On average, patients with AD live for 8 to 10 years after they
are diagnosed. However, some people live as long as 20 years.
Patients with AD often die of aspiration pneumonia because they lose
the ability to swallow late in the course of the disease.
Vascular dementia is the second most common
cause of dementia, after AD. It accounts for up to 20 percent of all
dementias and is caused by brain damage from cerebrovascular or
cardiovascular problems - usually strokes. It also may result from
genetic diseases, endocarditis (infection of a heart valve), or
amyloid angiopathy (a process in which amyloid protein builds up in
the brain's blood vessels, sometimes causing hemorrhagic or
"bleeding" strokes). In many cases, it may coexist with AD. The
incidence of vascular dementia increases with advancing age and is
similar in men and women.
Symptoms of vascular dementia often begin suddenly, frequently
after a stroke. Patients may have a history of high blood pressure,
vascular disease, or previous strokes or heart attacks. Vascular
dementia may or may not get worse with time, depending on whether
the person has additional strokes. In some cases, symptoms may get
better with time. When the disease does get worse, it often
progresses in a stepwise manner, with sudden changes in ability.
Vascular dementia with brain damage to the mid-brain regions,
however, may cause a gradual, progressive cognitive impairment that
may look much like AD. Unlike people with AD, people with vascular
dementia often maintain their personality and normal levels of
emotional responsiveness until the later stages of the disease.
People with vascular dementia frequently wander at night and
often have other problems commonly found in people who have had a
stroke, including depression and incontinence.
There are several types of vascular dementia, which vary slightly
in their causes and symptoms. One type, called multi-infarct
dementia (MID), is caused by numerous small strokes in the
brain. MID typically includes multiple damaged areas, called
infarcts, along with extensive lesions in the white matter, or nerve
fibers, of the brain.
Because the infarcts in MID affect isolated areas of the brain,
the symptoms are often limited to one side of the body or they may
affect just one or a few specific functions, such as language.
Neurologists call these "local" or "focal" symptoms, as opposed to
the "global" symptoms seen in AD, which affect many functions and
are not restricted to one side of the body.
Although not all strokes cause dementia, in some cases a single
stroke can damage the brain enough to cause dementia. This condition
is called single-infarct dementia. Dementia is more common when the
stroke takes place on the left side (hemisphere) of the brain and/or
when it involves the hippocampus, a brain structure important for
Another type of vascular dementia is called Binswanger's
disease. This rare form of dementia is characterized by damage
to small blood vessels in the white matter of the brain (white
matter is found in the inner layers of the brain and contains many
nerve fibers coated with a whitish, fatty substance called
myelin). Binswanger's disease leads to brain lesions, loss
of memory, disordered cognition, and mood changes. Patients with
this disease often show signs of abnormal blood pressure, stroke,
blood abnormalities, disease of the large blood vessels in the neck,
and/or disease of the heart valves. Other prominent features include
urinary incontinence, difficulty walking, clumsiness, slowness, lack
of facial expression, and speech difficulty. These symptoms, which
usually begin after the age of 60, are not always present in all
patients and may sometimes appear only temporarily. Treatment of
Binswanger's disease is symptomatic, and may include the use of
medications to control high blood pressure, depression, heart
arrhythmias, and low blood pressure. The disorder often includes
episodes of partial recovery.
Another type of vascular dementia is linked to a rare hereditary
disorder called CADASIL, which stands for
dominant arteriopathy with
subcortical infarct and
leukoencephalopathy. CADASIL is linked to
abnormalities of a specific gene, Notch3, which is located on
chromosome 19. This condition causes multi-infarct dementia as well
as stroke, migraine with aura, and mood disorders. The first
symptoms usually appear in people who are in their twenties,
thirties, or forties and affected individuals often die by age 65.
Researchers believe most people with CADASIL go undiagnosed, and the
actual prevalence of the disease is not yet known.
Other causes of vascular dementia include vasculitis, an
inflammation of the blood vessel system; profound hypotension (low
blood pressure); and lesions caused by brain hemorrhage. The
autoimmune disease lupus erythematosus and the inflammatory disease
temporal arteritis can also damage blood vessels in a way that leads
to vascular dementia.
Lewy body dementia (LBD) is one of the most
common types of progressive dementia. LBD usually occurs
sporadically, in people with no known family history of the disease.
However, rare familial cases have occasionally been reported.
In LBD, cells die in the brain's cortex, or outer layer, and in a
part of the mid-brain called the substantia nigra. Many of the
remaining nerve cells in the substantia nigra contain abnormal
structures called Lewy bodies that are the hallmark of the disease.
Lewy bodies may also appear in the brain's cortex, or outer layer.
Lewy bodies contain a protein called alpha-synuclein that has been
linked to Parkinson's disease and several other disorders.
Researchers, who sometimes refer to these disorders collectively as
"synucleinopathies," do not yet know why this protein accumulates
inside nerve cells in LBD.
The symptoms of LBD overlap with AD in many ways, and may include
memory impairment, poor judgment, and confusion. However, LBD
typically also includes visual hallucinations, parkinsonian symptoms
such as a shuffling gait and flexed posture, and day-to-day
fluctuations in the severity of symptoms. Patients with LBD live an
average of 7 years after symptoms begin.
There is no cure for LBD, and treatments are aimed at controlling
the parkinsonian and psychiatric symptoms of the disorder. Patients
sometimes respond dramatically to treatment with antiparkinsonian
drugs and/or cholinesterase inhibitors, such as those used
for AD. Some studies indicate that neuroleptic drugs, such as
clozapine and olanzapine, also can reduce the psychiatric symptoms
of this disease. But neuroleptic drugs may cause severe adverse
reactions, so other therapies should be tried first and patients
using these drugs should be closely monitored.
Lewy bodies are often found in the brains of people with
Parkinson's and AD. These findings suggest that either LBD is
related to these other causes of dementia or that the diseases
sometimes coexist in the same person.
Frontotemporal dementia (FTD), sometimes called
frontal lobe dementia, describes a group of diseases characterized
by degeneration of nerve cells - especially those in the frontal and
temporal lobes of the brain. Unlike AD, FTD usually does not include
formation of amyloid plaques. In many people with FTD, there is an
abnormal form of tau protein in the brain, which
accumulates into neurofibrillary tangles. This disrupts normal cell
activities and may cause the cells to die.
Experts believe FTD accounts for 2 to 10 percent of all cases of
dementia. Symptoms of FTD usually appear between the ages of 40 and
65. In many cases, people with FTD have a family history of
dementia, suggesting that there is a strong genetic factor in the
disease. The duration of FTD varies, with some patients declining
rapidly over 2 to 3 years and others showing only minimal changes
for many years. People with FTD live with the disease for an average
of 5 to 10 years after diagnosis.
Because structures found in the frontal and temporal lobes of the
brain control judgment and social behavior, people with FTD often
have problems maintaining normal interactions and following social
conventions. They may steal or exhibit impolite and socially
inappropriate behavior, and they may neglect their normal
responsibilities. Other common symptoms include loss of speech and
language, compulsive or repetitive behavior, increased appetite, and
motor problems such as stiffness and balance problems. Memory loss
also may occur, although it typically appears late in the
In one type of FTD called Pick's disease, certain nerve
cells become abnormal and swollen before they die. These swollen, or
ballooned, neurons are one hallmark of the disease. The brains of
people with Pick's disease also have abnormal structures called Pick
bodies, composed largely of the protein tau, inside the
neurons. The cause of Pick's disease is unknown, but it runs in some
families and thus it is probably due at least in part to a faulty
gene or genes. The disease usually begins after age 50 and causes
changes in personality and behavior that gradually worsen over time.
The symptoms of Pick's disease are very similar to those of AD, and
may include inappropriate social behavior, loss of mental
flexibility, language problems, and difficulty with thinking and
concentration. There is currently no way to slow the progressive
degeneration found in Pick's disease. However, medication may be
helpful in reducing aggression and other behavioral problems, and in
In some cases, familial FTD is linked to a mutation in the
tau gene. This disorder, called frontotemporal dementia
with parkinsonism linked to chromosome 17 (FTDP-17), is much
like other types of FTD but often includes psychiatric symptoms such
as delusions and hallucinations.
Primary progressive aphasia (PPA) is a type of FTD that
may begin in people as early as their forties. "Aphasia" is a
general term used to refer to deficits in language functions, such
as speaking, understanding what others are saying, and naming common
objects. In PPA one or more of these functions can become impaired.
Symptoms often begin gradually and progress slowly over a period of
years. As the disease progresses, memory and attention may also be
impaired and patients may show personality and behavior changes.
Many, but not all, people with PPA eventually develop symptoms of
HIV-associated dementia (HAD) results from
infection with the human immunodeficiency virus (HIV) that causes
AIDS. HAD can cause widespread destruction of the brain's white
matter. This leads to a type of dementia that generally includes
impaired memory, apathy, social withdrawal, and difficulty
concentrating. People with HAD often develop movement problems as
well. There is no specific treatment for HAD, but AIDS drugs can
delay onset of the disease and may help to reduce symptoms.
Huntington's disease (HD) is a hereditary
disorder caused by a faulty gene for a protein called huntingtin.
The children of people with the disorder have a 50 percent chance of
inheriting it. The disease causes degeneration in many regions of
the brain and spinal cord. Symptoms of HD usually begin when
patients are in their thirties or forties, and the average life
expectancy after diagnosis is about 15 years.
Cognitive symptoms of HD typically begin with mild personality
changes, such as irritability, anxiety, and depression, and progress
to severe dementia. Many patients also show psychotic behavior. HD
causes chorea - involuntary jerky, arrhythmic movements of the body
- as well as muscle weakness, clumsiness, and gait disturbances.
Dementia pugilistica, also called chronic
traumatic encephalopathy or Boxer's syndrome, is caused by
head trauma, such as that experienced by people who have been
punched many times in the head during boxing. The most common
symptoms of the condition are dementia and parkinsonism, which can
appear many years after the trauma ends. Affected individuals may
also develop poor coordination and slurred speech. A single
traumatic brain injury may also lead to a disorder called
post-traumatic dementia (PTD). PTD is much like dementia
pugilistica but usually also includes long-term memory problems.
Other symptoms vary depending on which part of the brain was damaged
by the injury.
Corticobasal degeneration (CBD) is a progressive
disorder characterized by nerve cell loss and atrophy of
multiple areas of the brain. Brain cells from people with CBD often
have abnormal accumulations of the protein tau. CBD usually
progresses gradually over the course of 6 to 8 years. Initial
symptoms, which typically begin at or around age 60, may first
appear on one side of the body but eventually will affect both
sides. Some of the symptoms, such as poor coordination and rigidity,
are similar to those found in Parkinson's disease. Other symptoms
may include memory loss, dementia, visual-spatial problems, apraxia
(loss of the ability to make familiar, purposeful movements),
hesitant and halting speech, myoclonus (involuntary
muscular jerks), and dysphagia (difficulty swallowing).
Death is often caused by pneumonia or other secondary problems such
as sepsis (severe infection of the blood) or pulmonary embolism (a
blood clot in the lungs).
There are no specific treatments available for CBD. Drugs such as
clonazepam may help with myoclonus, however, and occupational,
physical, and speech therapy can help in managing the disabilities
associated with this disease. The symptoms of the disease often do
not respond to Parkinson's medications or other drugs.
Creutzfeldt-Jakob disease (CJD) is a rare,
degenerative, fatal brain disorder that affects about one in every
million people per year worldwide. Symptoms usually begin after age
60 and most patients die within 1 year. Many researchers believe CJD
results from an abnormal form of a protein called a prion. Most
cases of CJD occur sporadically - that is, in people who have no
known risk factors for the disease. However, about 5 to 10 percent
of cases of CJD in the United States are hereditary, caused by a
mutation in the gene for the prion protein. In rare cases, CJD can
also be acquired through exposure to diseased brain or nervous
system tissue, usually through certain medical procedures. There is
no evidence that CJD is contagious through the air or through casual
contact with a CJD patient.
Patients with CJD may initially experience problems with muscular
coordination; personality changes, including impaired memory,
judgment, and thinking; and impaired vision. Other symptoms may
include insomnia and depression. As the illness progresses, mental
impairment becomes severe. Patients often develop myoclonus and they
may go blind. They eventually lose the ability to move and speak,
and go into a coma. Pneumonia and other infections often occur in
these patients and can lead to death.
CJD belongs to a family of human and animal diseases known as the
transmissible spongiform encephalopathies (TSEs).
Spongiform refers to the characteristic appearance of infected
brains, which become filled with holes until they resemble sponges
when viewed under a microscope. CJD is the most common of the known
human TSEs. Others include fatal familial insomnia and
Gerstmann-Straussler-Scheinker disease (see below).
In recent years, a new type of CJD, called variant CJD (vCJD),
has been found in Great Britain and several other European
countries. The initial symptoms of vCJD are different from those of
classic CJD and the disorder typically occurs in younger patients.
Research suggests that vCJD may have resulted from human consumption
of beef from cattle with a TSE disease called bovine spongiform
encephalopathy (BSE), also known as "mad cow disease."
Other rare hereditary dementias include
Gerstmann-Straussler-Scheinker (GSS) disease, fatal familial
insomnia, familial British dementia, and familial Danish dementia.
Symptoms of GSS typically include ataxia and progressive
dementia that begins when people are between 50 and 60 years old.
The disease may last for several years before patients eventually
die. Fatal familial insomnia causes degeneration of a brain region
called the thalamus, which is partially responsible for controlling
sleep. It causes a progressive insomnia that eventually leads to a
complete inability to sleep. Other symptoms may include poor
reflexes, dementia, hallucinations, and eventually coma. It can be
fatal within 7 to 13 months after symptoms begin but may last
longer. Familial British dementia and familial Danish dementia have
been linked to two different defects in a gene found on chromosome
13. The symptoms of both diseases include progressive dementia,
paralysis, and loss of balance.
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Dementia may occur in patients who have other disorders that
primarily affect movement or other functions. These cases are often
referred to as secondary dementias. The relationship between these
disorders and the primary dementias is not always clear. For
instance, people with advanced Parkinson's disease,
is primarily a movement disorder, sometimes develop symptoms of
dementia. Many Parkinson's patients also have amyloid plaques and
neurofibrillary tangles like those found in AD. The two diseases may
be linked in a yet-unknown way, or they may simply coexist in some
people. People with Parkinson's and associated dementia sometimes
show signs of Lewy body dementia or progressive supranuclear palsy
at autopsy, suggesting that these diseases may also overlap with
Parkinson's or that Parkinson's is sometimes misdiagnosed.
Other disorders that may include symptoms of dementia include
multiple sclerosis; presenile dementia with motor neuron disease,
also called ALS dementia; olivopontocerebellar atrophy (OPCA);
Wilson's disease; and normal pressure hydrocephalus (NPH).
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While it is usually found in adults, dementia can also occur in
children. For example, infections and poisoning can lead to dementia
in people of any age. In addition, some disorders unique to children
can cause dementia.
Niemann-Pick disease is a group of inherited
disorders that affect metabolism and are caused by specific genetic
mutations. Patients with Niemann-Pick disease cannot properly
metabolize cholesterol and other lipids. Consequently, excessive
amounts of cholesterol accumulate in the liver and spleen and
excessive amounts of other lipids accumulate in the brain. Symptoms
may include dementia, confusion, and problems with learning and
memory. These diseases usually begin in young school-age children
but may also appear during the teen years or early adulthood.
Batten disease is a fatal, hereditary disorder
of the nervous system that begins in childhood. Symptoms are linked
to a buildup of substances called lipopigments in the body's
tissues. The early symptoms include personality and behavior
changes, slow learning, clumsiness, or stumbling. Over time,
affected children suffer mental impairment, seizures, and
progressive loss of sight and motor skills. Eventually, children
with Batten disease develop dementia and become blind and bedridden.
The disease is often fatal by the late teens or twenties.
Lafora body disease is a rare genetic disease
that causes seizures, rapidly progressive dementia, and movement
problems. These problems usually begin in late childhood or the
early teens. Children with Lafora body disease have microscopic
structures called Lafora bodies in the brain, skin, liver, and
muscles. Most affected children die within 2 to 10 years after the
onset of symptoms.
A number of other childhood-onset disorders can include symptoms
of dementia. Among these are mitochondrial myopathies, Rasmussen's
encephalitis, mucopolysaccharidosis III (Sanfilippo syndrome),
neurodegeneration with brain iron accumulation, and leukodystrophies
such as Alexander disease, Schilder's disease, and metachromatic
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Doctors have identified many other conditions that can cause
dementia or dementia-like symptoms. Many of these conditions are
reversible with appropriate treatment.
Reactions to medications. Medications can
sometimes lead to reactions or side effects that mimic dementia.
These dementia-like effects can occur in reaction to just one drug
or they can result from drug interactions. They may have a rapid
onset or they may develop slowly over time.
Metabolic problems and endocrine abnormalities.
Thyroid problems can lead to apathy, depression, or dementia.
Hypoglycemia, a condition in which there is not enough sugar in the
bloodstream, can cause confusion or personality changes. Too little
or too much sodium or calcium can also trigger mental changes. Some
people have an impaired ability to absorb vitamin B12,
which creates a condition called pernicious anemia that can cause
personality changes, irritability, or depression. Tests can
determine if any of these problems are present.
Nutritional deficiencies. Deficiencies of
thiamine (vitamin B1) frequently result from chronic
alcoholism and can seriously impair mental abilities, in particular
memories of recent events. Severe deficiency of vitamin
B6 can cause a neurological illness called pellagra that
may include dementia. Deficiencies of vitamin B12 also
have been linked to dementia in some cases. Dehydration can also
cause mental impairment that can resemble dementia.
Infections. Many infections can cause
neurological symptoms, including confusion or delirium, due to fever
or other side effects of the body's fight to overcome the infection.
Meningitis and encephalitis, which are infections of the brain or
the membrane that covers it, can cause confusion, sudden severe
dementia, withdrawal from social interaction, impaired judgment, or
memory loss. Untreated syphilis also can damage the nervous system
and cause dementia. In rare cases, Lyme disease can cause memory or
thinking difficulties. People in the advanced stages of AIDS also
may develop a form of dementia (see HIV-associated
dementia, page 14). People with compromised immune systems, such as
those with leukemia and AIDS, may also develop an infection called
progressive multifocal leukoencephalopathy (PML). PML is caused by a
common human polyomavirus, JC virus, and leads to damage or
destruction of the myelin sheath that covers nerve cells. PML can
lead to confusion, difficulty with thinking or speaking, and other
Subdural hematomas. Subdural hematomas, or
bleeding between the brain's surface and its outer covering (the
dura), can cause dementia-like symptoms and changes in mental
Poisoning. Exposure to lead, other heavy metals,
or other poisonous substances can lead to symptoms of dementia.
These symptoms may or may not resolve after treatment, depending on
how badly the brain is damaged. People who have abused substances
such as alcohol and recreational drugs sometimes display signs of
dementia even after the substance abuse has ended. This condition is
known as substance-induced persisting dementia.
Brain tumors. In rare cases, people with brain
tumors may develop dementia because of damage to their brains.
Symptoms may include changes in personality, psychotic episodes, or
problems with speech, language, thinking, and memory.
Anoxia. Anoxia and a related term, hypoxia, are
often used interchangeably to describe a state in which there is a
diminished supply of oxygen to an organ's tissues. Anoxia may be
caused by many different problems, including heart attack, heart
surgery, severe asthma, smoke or carbon monoxide inhalation,
high-altitude exposure, strangulation, or an overdose of anesthesia.
In severe cases of anoxia the patient may be in a stupor or a coma
for periods ranging from hours to days, weeks, or months. Recovery
depends on the severity of the oxygen deprivation. As recovery
proceeds, a variety of psychological and neurological abnormalities,
such as dementia or psychosis, may occur. The person also may
experience confusion, personality changes, hallucinations, or memory
Heart and lung problems. The brain requires a
high level of oxygen in order to carry out its normal functions.
Therefore, problems such as chronic lung disease or heart problems
that prevent the brain from receiving adequate oxygen can starve
brain cells and lead to the symptoms of dementia.
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Age-related cognitive decline. As people age,
they usually experience slower information processing and mild
memory impairment. In addition, their brains frequently decrease in
volume and some nerve cells, or neurons, are lost. These changes,
called age-related cognitive decline, are normal and are not
considered signs of dementia.
Mild cognitive impairment. Some people develop
cognitive and memory problems that are not severe enough to be
diagnosed as dementia but are more pronounced than the cognitive
changes associated with normal aging. This condition is called
mild cognitive impairment. Although many patients with this
condition later develop dementia, some do not. Many researchers are
studying mild cognitive impairment to find ways to treat it or
prevent it from progressing to dementia.
Depression. People with depression are
frequently passive or unresponsive, and they may appear slow,
confused, or forgetful. Other emotional problems can also cause
symptoms that sometimes mimic dementia.
Delirium. Delirium is characterized by confusion
and rapidly altering mental states. The person may also be
disoriented, drowsy, or incoherent, and may exhibit personality
changes. Delirium is usually caused by a treatable physical or
psychiatric illness, such as poisoning or infections. Patients with
delirium often, though not always, make a full recovery after their
underlying illness is treated.
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death of nerve cells and/or
the loss of communication among these cells. The human brain is a
very complex and intricate machine and many factors can interfere
with its functioning. Researchers have uncovered many of these
factors, but they have not yet been able to fit these puzzle pieces
together in order to form a complete picture of how dementias
Many types of dementia, including AD, Lewy body dementia,
Parkinson's dementia, and Pick's disease, are characterized by
abnormal structures called inclusions in the brain. Because these
inclusions, which contain abnormal proteins, are so common in people
with dementia, researchers suspect that they play a role in the
development of symptoms. However, that role is unknown, and in some
cases the inclusions may simply be a side effect of the disease
process that leads to the dementia.
Genes clearly play a role in the development of some kinds of
dementia. However, in AD and many other disorders, the dementia
usually cannot be tied to a single abnormal gene. Instead, these
forms of dementia appear to result from a complex interaction of
genes, lifestyle factors, and other environmental influences.
Researchers have identified several genes that influence
susceptibility to AD. Mutations in three of the known genes for AD -
genes that control the production of proteins such as amyloid
precursor protein (APP), presenilin 1, and
presenilin 2 - are linked to early-onset forms of the
Variations in another gene, called apolipoprotein E
(apoE), have been linked to an increased risk of late-onset AD. The
apoE gene does not cause the disease by itself, but one version of
the gene, called apoE epsilon4 (apoE E4), appears to increase the
risk of AD. People with two copies of the apoE E4 gene have about
ten times the risk of developing AD compared to people without apoE
E4. This gene variant seems to encourage amyloid deposition in the
brain. One study also found that this gene is associated with
shorter survival in men with AD. In contrast, another version of the
apoE gene, called apoE E2, appears to protect against AD.
Studies have suggested that mutations in another gene, called
CYP46, may contribute to an increased risk of developing late-onset
sporadic AD. This gene normally produces a protein that helps the
brain metabolize cholesterol.
Scientists are trying to determine how beta amyloid influences
the development of AD. A number of studies indicate that the buildup
of this protein initiates a complex chain of events that culminates
in dementia. One study found that beta amyloid buildup in the brain
triggers cells called microglia, which act like janitors that mop up
potentially harmful substances in the brain, to release a potent
neurotoxin called peroxynitrite. This may contribute to nerve cell
death in AD. Another study found that beta amyloid causes a protein
called p35 to be split into two proteins. One of the resulting
proteins triggers changes in the tau protein that lead to
formation of neurofibrillary tangles. A third study found that beta
amyloid activates cell-death enzymes called caspases that alter the
tau protein in a way that causes it to form tangles.
Researchers believe these tangles may contribute to the neuron death
Vascular dementia can be caused by cerebrovascular disease or any
other condition that prevents normal blood flow to the brain.
Without a normal supply of blood, brain cells cannot obtain the
oxygen they need to work correctly, and they often become so
deprived that they die.
The causes of other types of dementias vary. Some, such as CJD
and GSS, have been tied to abnormal forms of specific proteins.
Others, including Huntington's disease and FTDP-17, have been linked
to defects in a single gene. Post-traumatic dementia is directly
related to brain cell death after injury. HIV-associated dementia is
clearly tied to infection by the HIV virus, although the exact way
the virus causes damage is not yet certain. For other dementias,
such as corticobasal degeneration and most types of frontotemporal
dementia, the underlying causes have not yet been identified.
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Researchers have identified several risk factors that affect the
likelihood of developing one or more kinds of dementia. Some of
these factors are modifiable, while others are not.
Age. The risk of AD, vascular dementia,
and several other dementias goes up significantly with advancing
Genetics/family history. As described
in the section "What Causes Dementia?" researchers have discovered a
number of genes that increase the risk of developing AD. Although
people with a family history of AD are generally considered to be at
heightened risk of developing the disease themselves, many people
with a family history never develop the disease, and many without a
family history of the disease do get it. In most cases, it is still
impossible to predict a specific person's risk of the disorder based
on family history alone. Some families with CJD, GSS, or fatal
familial insomnia have mutations in the prion protein gene, although
these disorders can also occur in people without the gene mutation.
Individuals with these mutations are at significantly higher risk of
developing these forms of dementia. Abnormal genes are also clearly
implicated as risk factors in Huntington's disease, FTDP-17, and
several other kinds of dementia. These dementias are described in
the section "What are the different kinds of dementia?"
Smoking and alcohol use. Several recent
studies have found that smoking significantly increases the risk of
mental decline and dementia. People who smoke have a higher risk of
atherosclerosis and other types of vascular disease, which
may be the underlying causes for the increased dementia risk.
Studies also have found that drinking large amounts of alcohol
appears to increase the risk of dementia. However, other studies
have suggested that people who drink moderately have a lower risk of
dementia than either those who drink heavily or those who completely
abstain from drinking.
Atherosclerosis. Atherosclerosis is the
buildup of plaque - deposits of fatty substances, cholesterol, and
other matter - in the inner lining of an artery. Atherosclerosis is
a significant risk factor for vascular dementia, because it
interferes with the delivery of blood to the brain and can lead to
stroke. Studies have also found a possible link between
atherosclerosis and AD.
Cholesterol. High levels of low-density
lipoprotein (LDL), the so-called bad form of cholesterol, appear to
significantly increase a person's risk of developing vascular
dementia. Some research has also linked high cholesterol to an
increased risk of AD.
Plasma homocysteine. Research has shown
that a higher-than-average blood level of homocysteine - a type of
amino acid - is a strong risk factor for the development of AD and
Diabetes. Diabetes is a risk factor for
both AD and vascular dementia. It is also a known risk factor for
atherosclerosis and stroke, both of which contribute to vascular
Mild cognitive impairment. While not
all people with mild cognitive impairment develop dementia, people
with this condition do have a significantly increased risk of
dementia compared to the rest of the population. One study found
that approximately 40 percent of people over age 65 who were
diagnosed with mild cognitive impairment developed dementia within 3
Down syndrome. Studies have found that
most people with Down syndrome develop characteristic AD plaques and
neurofibrillary tangles by the time they reach middle age. Many, but
not all, of these individuals also develop symptoms of dementia.
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Doctors employ a number of strategies to diagnose dementia. It is
important that they rule out any treatable conditions, such as
depression, normal pressure hydrocephalus, or vitamin B12
deficiency, which can cause similar symptoms.
Early, accurate diagnosis of dementia is important for patients
and their families because it allows early treatment of symptoms.
For people with AD or other progressive dementias, early diagnosis
may allow them to plan for the future while they can still help to
make decisions. These people also may benefit from drug
The "gold standard" for diagnosing dementia, autopsy, does not
help the patient or caregivers. Therefore, doctors have devised a
number of techniques to help identify dementia with reasonable
accuracy while the patient is still alive.
Doctors often begin
their examination of a patient suspected of having dementia by
asking questions about the patient's history. For example, they may
ask how and when symptoms developed and about the patient's overall
medical condition. They also may try to evaluate the patient's
emotional state, although patients with dementia often may be
unaware of or in denial about how their disease is affecting them.
Family members also may deny the existence of the disease because
they do not want to accept the diagnosis and because, at least in
the beginning, AD and other forms of dementia can resemble normal
aging. Therefore additional steps are necessary to confirm or rule
out a diagnosis of dementia.
examination can help rule out treatable causes of dementia and
identify signs of stroke or other disorders that can contribute to
dementia. It can also identify signs of other illnesses, such as
heart disease or kidney failure, that can overlap with dementia. If
a patient is taking medications that may be causing or contributing
to his or her symptoms, the doctor may suggest stopping or replacing
some medications to see if the symptoms go away.
will perform a neurological examination, looking at balance, sensory
function, reflexes, and other functions, to identify signs of
conditions - for example movement disorders or stroke - that may
affect the patient's diagnosis or are treatable with drugs.
Cognitive and neuropsychological
Doctors use tests that measure memory,
language skills, math skills, and other abilities related to mental
functioning to help them diagnose a patient's condition accurately.
For example, people with AD often show changes in so-called
executive functions (such as problem-solving), memory, and the
ability to perform once-automatic tasks.
Doctors often use a test called the Mini-Mental State
Examination (MMSE) to assess cognitive skills in people with
suspected dementia. This test examines orientation, memory, and
attention, as well as the ability to name objects, follow verbal and
written commands, write a sentence spontaneously, and copy a complex
shape. Doctors also use a variety of other tests and rating scales
to identify specific types of cognitive problems and abilities.
Doctors may use brain
scans to identify strokes, tumors, or other problems that can cause
dementia. Also, cortical atrophy -degeneration of the
brain's cortex (outer layer) - is common in many forms of dementia
and may be visible on a brain scan. The brain's cortex normally
appears very wrinkled, with ridges of tissue (called gyri) separated
by "valleys" called sulci. In individuals with cortical atrophy, the
progressive loss of neurons causes the ridges to become thinner and
the sulci to grow wider. As brain cells die, the ventricles (or
fluid-filled cavities in the middle of the brain) expand to fill the
available space, becoming much larger than normal. Brain scans also
can identify changes in the brain's structure and function that
The most common types of brain scans are computed tomographic
(CT) scans and magnetic resonance imaging (MRI).
Doctors frequently request a CT scan of the brain when they are
examining a patient with suspected dementia. These scans, which use
X-rays to detect brain structures, can show evidence of brain
atrophy, strokes and transient ischemic attacks (TIAs), changes to
the blood vessels, and other problems such as hydrocephalus and
subdural hematomas. MRI scans use magnetic fields and focused radio
waves to detect hydrogen atoms in tissues within the body. They can
detect the same problems as CT scans but they are better for
identifying certain conditions, such as brain atrophy and damage
from small TIAs.
Doctors also may use electroencephalograms (EEGs) in
people with suspected dementia. In an EEG, electrodes are placed on
the scalp over several parts of the brain in order to detect and
record patterns of electrical activity and check for abnormalities.
This electrical activity can indicate cognitive dysfunction in part
or all of the brain. Many patients with moderately severe to severe
AD have abnormal EEGs. An EEG may also be used to detect seizures,
which occur in about 10 percent of AD patients as well as in many
other disorders. EEGs also can help diagnose CJD.
Several other types of brain scans allow researchers to watch the
brain as it functions. These scans, called functional brain imaging,
are not often used as diagnostic tools, but they are important in
research and they may ultimately help identify people with dementia
earlier than is currently possible. Functional brain scans include
functional MRI (fMRI), single photon-emission computed tomography
(SPECT), positron emission tomography (PET), and
magnetoencephalography (MEG). fMRI uses radio waves and a strong
magnetic field to measure the metabolic changes that take place in
active parts of the brain. SPECT shows the distribution of blood in
the brain, which generally increases with brain activity. PET scans
can detect changes in glucose metabolism, oxygen metabolism, and
blood flow, all of which can reveal abnormalities of brain function.
MEG shows the electromagnetic fields produced by the brain's
Doctors may use a
variety of laboratory tests to help diagnose dementia and/or rule
out other conditions, such as kidney failure, that can contribute to
symptoms. A partial list of these tests includes a complete blood
count, blood glucose test, urinalysis, drug and alcohol tests
(toxicology screen), cerebrospinal fluid analysis (to rule out
specific infections that can affect the brain), and analysis of
thyroid and thyroid-stimulating hormone levels. A doctor will order
only the tests that he or she feels are necessary and/or likely to
improve the accuracy of a diagnosis.
evaluation may be obtained to determine if depression or another
psychiatric disorder may be causing or contributing to a person's
people before symptoms begin to determine if they will develop
dementia is not possible in most cases. However, in disorders such
as Huntington's where a known gene defect is clearly linked to the
risk of the disease, a genetic test can help identify people who are
likely to develop the disease. Since this type of genetic
information can be devastating, people should carefully consider
whether they want to undergo such testing.
Researchers are examining whether a series of simple cognitive
tests, such as matching words with pictures, can predict who will
develop dementia. One study suggested that a combination of a verbal
learning test and an odor-identification test can help identify AD
before symptoms become obvious. Other studies are looking at whether
memory tests and brain scans can be useful indicators of future
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While treatments to reverse or halt disease progression are not
available for most of the dementias, patients can benefit to some
extent from treatment with available medications and other measures,
such as cognitive training
Drugs to specifically treat AD and some other progressive
dementias are now available and are prescribed for many patients.
Although these drugs do not halt the disease or reverse existing
brain damage, they can improve symptoms and slow the progression of
the disease. This may improve the patient's quality of life, ease
the burden on caregivers, and/or delay admission to a nursing home.
Many researchers are also examining whether these drugs may be
useful for treating other types of dementia.
Many people with dementia, particularly those in the early
stages, may benefit from practicing tasks designed to improve
performance in specific aspects of cognitive functioning. For
example, people can sometimes be taught to use memory aids, such as
mnemonics, computerized recall devices, or note taking.
Behavior modification - rewarding appropriate or positive
behavior and ignoring inappropriate behavior - also may help control
unacceptable or dangerous behaviors.
Most of the
drugs currently approved by the U. S. Food and Drug Administration
for AD fall into a category called cholinesterase inhibitors. These
drugs slow the breakdown of the neurotransmitter
acetylcholine, which is reduced in the brains of people with
AD. Acetylcholine is important for the formation of memories and it
is used in the hippocampus and the cerebral cortex, two brain
regions that are affected by AD. There are currently four
cholinesterase inhibitors approved for use in the United
States:tacrine (Cognex), donepezil (Aricept), rivastigmine (Exelon),
and galantamine (Reminyl). These drugs temporarily improve or
stabilize memory and thinking skills in some individuals. Many
studies have shown that cholinesterase inhibitors help to slow the
decline in mental functions associated with AD, and that they can
help reduce behavioral problems and improve the ability to perform
everyday tasks. However, none of these drugs can stop or reverse the
course of AD.
A fifth drug, memantine (Namenda), was recently approved for use
in the United States. Unlike other drugs for AD, which affect
acetylcholine levels, memantine works by regulating the activity of
a neurotransmitter called glutamate that plays a role in learning
and memory. Glutamate activity is often disrupted in AD. Because
this drug works differently from cholinesterase inhibitors,
combining memantine with other AD drugs may be more effective than
any single therapy. One controlled clinical trial found that
patients receiving donepezil plus memantine had better cognition and
other functions than patients receiving donepezil alone.
Doctors may also prescribe other drugs, such as anticonvulsants,
antipsychotics, sedatives, and antidepressants, to treat seizures,
depression, agitation, sleep disorders, and other specific problems
that can be associated with dementia.
There is no
standard drug treatment for vascular dementia, although some of the
symptoms, such as depression, can be treated. Most other treatments
aim to reduce the risk factors for further brain damage. However,
some studies have found that cholinesterase inhibitors, such as
galantamine and other AD drugs, can improve cognitive function and
behavioral symptoms in patients with early vascular dementia.
The progression of vascular dementia can often be slowed
significantly or halted if the underlying vascular risk factors for
the disease are treated. To prevent strokes and TIAs, doctors may
prescribe medicines to control high blood pressure, high
cholesterol, heart disease, and diabetes. Doctors also sometimes
prescribe aspirin, warfarin, or other drugs to prevent clots from
forming in small blood vessels. When patients have blockages in
blood vessels, doctors may recommend surgical procedures, such as
carotid endarterectomy, stenting, or angioplasty, to restore the
normal blood supply. Medications to relieve restlessness or
depression or to help patients sleep better may also be
Some studies have
suggested that cholinesterase inhibitors, such as donepezil
(Aricept), can reduce behavioral symptoms in some patients with
At present, no medications are approved specifically to treat or
prevent FTD and most other types of progressive dementia. However,
sedatives, antidepressants, and other medications may be useful in
treating specific symptoms and behavioral problems associated with
Scientists continue to search for specific treatments to help
people with Lewy body dementia. Current treatment is symptomatic,
often involving the use of medication to control the parkinsonian
and psychiatric symptoms. Although antiparkinsonian medication may
help reduce tremor and loss of muscle movement, it may worsen
symptoms such as hallucinations and delusions. Also, drugs
prescribed for psychiatric symptoms may make the movement problems
worse. In general, newer antipsychotic medications are more
successful than older drugs such as haloperidol. Several studies
have suggested that cholinesterase inhibitors may be able to improve
cognitive function and behavioral symptoms in patients with Lewy
There is no known treatment that can cure or control CJD. Current
treatment is aimed at alleviating symptoms and making the patient as
comfortable as possible. Opiate drugs can help relieve pain, and the
drugs clonazepam and sodium valproate may help relieve myoclonus.
During later stages of the disease, treatment focuses on supportive
care, such as administering intravenous fluids and changing the
person's position frequently to prevent bedsores.
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Research has revealed a number of factors that may be able to
prevent or delay the onset of dementia in some people. For example,
studies have shown that people who maintain tight control over their
glucose levels tend to score better on tests of cognitive function
than those with poorly controlled diabetes. Several studies also
have suggested that people who engage in intellectually stimulating
activities, such as social interactions, chess, crossword puzzles,
and playing a musical instrument, significantly lower their risk of
developing AD and other forms of dementia. Scientists believe mental
activities may stimulate the brain in a way that increases the
person's "cognitive reserve" - the ability to cope with or
compensate for the pathologic changes associated with dementia.
Researchers are studying other steps people can take that may
help prevent AD in some cases. So far, none of these factors has
been definitively proven to make a difference in the risk of
developing the disease. Moreover, most of the studies addressed only
AD, and the results may or may not apply to other forms of dementia.
Nevertheless, scientists are encouraged by the results of these
early studies and many believe it will eventually become possible to
prevent some forms of dementia. Possible preventive actions
- Lowering homocysteine. In one study, elevated blood
levels of the amino acid homocysteine were associated with a 2.9
times greater risk of AD and a 4.9 times greater risk of vascular
dementia. A preliminary study has shown that high doses of three B
vitamins that help lower homocysteine levels - folic acid,
B12, and B6 - appear to slow the progression
of AD. Researchers are now conducting a multi-center clinical
trial to test this effect in a larger group of patients.
- Lowering cholesterol levels. Research has suggested
that people with high cholesterol levels have an increased risk of
developing AD. Cholesterol is involved in formation of amyloid
plaques in the brain. Mutations in a gene called CYP46 and the
apoE E4 gene variant, both of which have been linked to an
increased risk of AD, are also involved in cholesterol metabolism.
Several studies have also found that the use of drugs called
statins, which lower cholesterol levels, is associated with a
lower likelihood of cognitive impairment.
- Lowering blood pressure. Several studies have shown
that antihypertensive medicine reduces the odds of cognitive
impairment in elderly people with high blood pressure. One large
European study found a 55 percent lower risk of dementia in people
over 60 who received drug treatment for hypertension. These people
had a reduced risk of both AD and vascular dementia.
- Exercise. Regular exercise stimulates production of
chemicals called growth factors that help neurons survive and
adapt to new situations. These gains may help to delay the onset
of dementia symptoms. Exercise also may reduce the risk of brain
damage from atherosclerosis.
- Education. Researchers have found evidence that
formal education may help protect people against the effects of
AD. In one study, researchers found that people with more years of
formal education had relatively less mental decline than people
with less schooling, regardless of the number of amyloid plaques
and neurofibrillary tangles each person had in his or her brain.
The researchers think education may cause the brain to develop
robust nerve cell networks that can help compensate for the cell
damage caused by AD.
- Controlling inflammation. Many studies have suggested
that inflammation may contribute to AD. Moreover, autopsies of
people who died with AD have shown widespread inflammation in the
brain that appeared to be caused by the accumulation of beta
amyloid. Another study found that men with high levels of
C-reactive protein, a general marker of inflammation, had a
significantly increased risk of AD and other kinds of dementia.
- Nonsteroidal anti-inflammatory drugs (NSAIDs).
Research indicates that long-term use of NSAIDs - ibuprofen,
naproxen, and similar drugs - may prevent or delay the onset of
AD. Researchers are not sure how these drugs may protect against
the disease, but some or all of the effect may be due to reduced
inflammation. A 2003 study showed that these drugs also bind to
amyloid plaques and may help to dissolve them and prevent
formation of new plaques.
The risk of vascular dementia is strongly correlated with risk
factors for stroke, including high blood pressure, diabetes,
elevated cholesterol levels, and smoking. This type of dementia may
be prevented in many cases by changing lifestyle factors, such as
excessive weight and high blood pressure, which are associated with
an increased risk of cerebrovascular disease. One European study
found that treating isolated systolic hypertension (high blood
pressure in which only the systolic or top number is high) in people
age 60 and older reduced the risk of dementia by 50 percent. These
studies strongly suggest that effective use of current treatments
can prevent many future cases of vascular dementia.
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People with moderate and advanced dementia typically need
round-the-clock care and supervision to prevent them from harming
themselves or others. They also may need assistance with daily
activities such as eating, bathing, and dressing. Meeting these
needs takes patience, understanding, and careful thought by the
A typical home environment can present many dangers and obstacles
to a person with dementia, but simple changes can overcome many of
these problems. For example, sharp knives, dangerous chemicals,
tools, and other hazards should be removed or locked away. Other
safety measures include installing bed and bathroom safety rails,
removing locks from bedroom and bathroom doors, and lowering the hot
water temperature to 120°F (48. 9°C) or less to reduce the risk of
accidental scalding. People with dementia also should wear some form
of identification at all times in case they wander away or become
lost. Caregivers can help prevent unsupervised wandering by adding
locks or alarms to outside doors.
People with dementia often develop behavior problems because of
frustration with specific situations. Understanding and modifying or
preventing the situations that trigger these behaviors may help to
make life more pleasant for the person with dementia as well as his
or her caregivers. For instance, the person may be confused or
frustrated by the level of activity or noise in the surrounding
environment. Reducing unnecessary activity and noise (such as
limiting the number of visitors and turning off the television when
it's not in use) may make it easier for the person to understand
requests and perform simple tasks. Confusion also may be reduced by
simplifying home decorations, removing clutter, keeping familiar
objects nearby, and following a predictable routine throughout the
day. Calendars and clocks also may help patients orient
People with dementia should be encouraged to continue their
normal leisure activities as long as they are safe and do not cause
frustration. Activities such as crafts, games, and music can provide
important mental stimulation and improve mood. Some studies have
suggested that participating in exercise and intellectually
stimulating activities may slow the decline of cognitive function in
Many studies have found that driving is unsafe for people with
dementia. They often get lost and they may have problems remembering
or following rules of the road. They also may have difficulty
processing information quickly and dealing with unexpected
circumstances. Even a second of confusion while driving can lead to
an accident. Driving with impaired cognitive functions can also
endanger others. Some experts have suggested that regular screening
for changes in cognition might help to reduce the number of driving
accidents among elderly people, and some states now require that
doctors report people with AD to their state motor vehicle
department. However, in many cases, it is up to the person's family
and friends to ensure that the person does not drive.
The emotional and physical burden of caring for someone with
dementia can be overwhelming. Support groups can often help
caregivers deal with these demands and they can also offer helpful
information about the disease and its treatment. It is important
that caregivers occasionally have time off from round-the-clock
nursing demands. Some communities provide respite facilities or
adult day care centers that will care for dementia patients for a
period of time, giving the primary caregivers a break. Eventually,
many patients with dementia require the services of a full-time
A list of caregiver organizations and support groups is included
at the end of this booklet.
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Current research focuses on many different aspects of dementia.
This research promises to improve the lives of people affected by
the dementias and may eventually lead to ways of preventing or
curing these disorders.
Causes and prevention
the causes of AD and other dementias includes studies of genetic
factors, neurotransmitters, inflammation, factors that influence
programmed cell death in the brain, and the roles of tau,
beta amyloid, and the associated neurofibrillary tangles and plaques
in AD. Some other researchers are trying to determine the possible
roles of cholesterol metabolism, oxidative stress (chemical
reactions that can damage proteins, DNA, and lipids inside cells),
and microglia in the development of AD. Scientists also are
investigating the role of aging-related proteins such as the enzyme
Since many dementias and other neurodegenerative diseases have
been linked to abnormal clumps of proteins in cells, researchers are
trying to learn how these clumps develop, how they affect cells, and
how the clumping can be prevented.
Some studies are examining whether changes in white matter -
nerve fibers lined with myelin - may play a role in the onset of AD.
Myelin may erode in AD patients before other changes occur. This may
be due to a problem with oligodendrocytes, the cells that produce
Researchers are searching for additional genes that may
contribute to AD, and they have identified a number of gene regions
that may be involved. Some researchers suggest that people will
eventually be screened for a number of genes that contribute to AD
and that they will be able to receive treatments that specifically
address their individual genetic risks. However, such individualized
screening and treatment is still years away.
Insulin resistance is common in people with AD, but it is not
clear whether the insulin resistance contributes to the development
of the disease or if it is merely a side effect.
Several studies have found a reduced risk of dementia in people
who take cholesterol-lowering drugs called statins. However, it is
not yet clear if the apparent effect is due to the drugs or to other
One clinical trial is testing estrogen to see if it can help
prevent AD. Early studies of estrogen looked promising. However, a
clinical study of several thousand postmenopausal women aged 65 or
older found that combination therapy with estrogen and progestin
substantially increased the risk of AD. The study is continuing to
examine whether taking estrogen alone may decrease the risk of
A 2003 study found that people with HIV-associated dementia have
different levels of activity for more than 30 different proteins,
compared to people who have HIV but no signs of dementia. The study
suggests a possible way to screen HIV patients for the first signs
of cognitive impairment, and it may lead to ways of intervening to
prevent this form of dementia.
Improving early diagnosis
of AD and other types of dementia is important not only for patients
and families, but also for researchers who seek to better understand
the causes of dementing diseases and find ways to reverse or halt
them at early stages. Improved diagnosis can also reduce the risk
that people will receive inappropriate treatments.
Some researchers are investigating whether three-dimensional
computer models of PET and MRI images can identify brain changes
typical of early AD, before any symptoms appear. This research may
lead to ways of preventing the symptoms of the disease.
One study found that levels of beta amyloid and tau in
spinal fluid can be used to diagnose AD with a sensitivity of 92
percent. If other studies confirm the validity of this test, it may
allow doctors to identify people who are beginning to develop the
disorder before they start to show symptoms. This would allow
treatment at very early stages of the disorder, and may help in
testing new treatments to prevent or delay symptoms of the disease.
Other researchers have identified factors in the skin and blood of
AD patients that are different from those in healthy people. They
are trying to determine if these factors can be used to diagnose the
continually working to develop new drugs for AD and other types of
dementia. Many researchers believe a vaccine that reduces the number
of amyloid plaques in the brain might ultimately prove to be the
most effective treatment for AD. In 2001, researchers began one
clinical trial of a vaccine called AN-1792. The study was halted
after a number of people developed inflammation of the brain and
spinal cord. Despite these problems, one patient appeared to have
reduced numbers of amyloid plaques in the brain. Other patients
showed little or no cognitive decline during the course of the
study, suggesting that the vaccine may slow or halt the disease.
Researchers are now trying to find safer and more effective vaccines
Researchers are also investigating possible methods of gene
therapy for AD. In one case, researchers used cells genetically
engineered to produce nerve growth factor and transplanted them into
monkeys' forebrains. The transplanted cells boosted the amount of
nerve growth factors in the brain and seemed to prevent degeneration
of acetylcholine-producing neurons in the animals. This suggests
that gene therapy might help to reduce or delay symptoms of the
disease. Researchers are now testing a similar therapy in a small
number of patients. Other researchers have experimented with gene
therapy that adds a gene called neprilysin in a mouse model that
produces human beta amyloid. They found that increasing the level of
neprilysin greatly reduced the amount of beta amyloid in the mice
and halted the amyloid-related brain degeneration. They are now
trying to determine whether neprilysin gene therapy can improve
cognition in mice.
A clinical trial called the Vitamins to Slow Alzheimer's Disease
(VITAL) study is testing whether high doses of three common B
vitamins - folic acid, B12, and B6 - can
reduce homocysteine levels and slow the rate of cognitive decline in
Since many studies have found evidence of brain inflammation in
AD, some researchers have proposed that drugs that control
inflammation, such as NSAIDs, might prevent the disease or slow its
progression. Studies in mice have suggested that these drugs can
limit production of amyloid plaques in the brain. Clinical trials
are now studying whether NSAIDs and related drugs can slow or
prevent development of AD in humans.
Other clinical trials for AD are investigating whether
antipsychotic drugs are useful in treating symptoms of AD, whether
use of a shunt to increase the flow of cerebrospinal fluid and
improve clearance of potential neurotoxins can halt or slow
progression of the disease, and whether insulin-sensitizing drugs
may be useful in treating AD.
Some researchers are investigating the effects of two drugs,
pentoxifylline and propentofylline, to treat vascular dementia.
Pentoxifylline improves blood flow, while propentofylline appears to
interfere with some of the processes that cause cell death in the
One study is testing the safety and effectiveness of donepezil
(Aricept) for treating mild dementia in patients with Parkinson's
dementia, while another is investigating whether skin patches with
the drug selegiline can improve mental function in patients with
cognitive problems related to HIV.
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acetylcholine - a neurotransmitter that is
important for the formation of memories. Studies have shown that
levels of acetylcholine are reduced in the brains of people with
Alzheimer's disease - the most common cause of
dementia in people aged 65 and older. Nearly all brain functions,
including memory, movement, language, judgment, behavior, and
abstract thinking, are eventually affected.
amyloid plaques - unusual clumps of material
found in the tissue between nerve cells. Amyloid plaques, which
consist of a protein called beta amyloid along with degenerating
bits of neurons and other cells, are a hallmark of Alzheimer's
amyloid precursor protein - a normal brain
protein that is a precursor for beta amyloid, the abnormal substance
found in the characteristic amyloid plaques of Alzheimer's disease
apolipoprotein E - a gene that has been linked
to an increased risk of Alzheimer's disease. People with a variant
form of the gene, called apoE epsilon 4, have about ten times the
risk of developing Alzheimer's disease.
ataxia - a loss of muscle control.
atherosclerosis - a blood vessel disease
characterized by the buildup of plaque, or deposits of fatty
substances and other matter in the inner lining of an artery.
beta amyloid - a protein found in the
characteristic clumps of tissue (called plaques) that appear in the
brains of Alzheimer's patients.
Binswanger's disease - a rare form of dementia
characterized by damage to small blood vessels in the white matter
of the brain. This damage leads to brain lesions, loss of memory,
disordered cognition, and mood changes.
CADASIL - a rare hereditary disorder which is
linked to a type of vascular dementia. It stands for
dominant arteriopathy with
subcortical infarct and
cholinesterase inhibitors - drugs that slow the
breakdown of the neurotransmitter acetylcholine.
cognitive training - a type of training in which
patients practice tasks designed to improve mental performance.
Examples include memory aids, such as mnemonics, and computerized
computed tomographic (CT) scans - a type of
brain scan that uses X-rays to detect brain structures.
cortical atrophy - degeneration of the brain's
cortex (outer layer). Cortical atrophy is common in many forms of
dementia and may be visible on a brain scan.
cortical dementia - a type of dementia in which
the damage primarily occurs in the brain's cortex, or outer
corticobasal degeneration - a progressive
disorder characterized by nerve cell loss and atrophy in multiple
areas of the brain.
Creutzfeldt-Jakob disease - a rare,
degenerative, fatal brain disorder believed to be linked to an
abnormal form of a protein called a prion.
dementia -a term for a collection of symptoms
that significantly impair thinking and normal activities and
dementia pugilistica - a form of dementia caused
by head trauma such as that experienced by boxers. It is also called
chronic traumatic encephalopathy or Boxer's syndrome.
electroencephalogram (EEG) - a medical procedure
that records patterns of electrical activity in the brain.
fatal familial insomnia - an inherited disease
that affects a brain region called the thalamus, which is partially
responsible for controlling sleep. The disease causes dementia and a
progressive insomnia that eventually leads to a complete lack of
frontotemporal dementias - a group of dementias
characterized by degeneration of nerve cells, especially those in
the frontal and temporal lobes of the brain.
FTDP-17 - one of the frontotemporal dementias,
linked to a mutation in the tau gene. It is much like other
types of the frontotemporal dementias but often includes psychiatric
symptoms such as delusions and hallucinations.
Gerstmann-Straussler-Scheinker disease - a rare,
fatal hereditary disease that causes ataxia and progressive
HIV-associated dementia - a dementia that
results from infection with the human immunodeficiency virus (HIV)
that causes AIDS. It can cause widespread destruction of the brain's
Huntington's disease - a degenerative hereditary
disorder caused by a faulty gene for a protein called huntington.
The disease causes degeneration in many regions of the brain and
spinal cord and patients eventually develop severe dementia.
Lewy body dementia - one of the most common
types of progressive dementia, characterized by the presence of
abnormal structures called Lewy bodies in the brain. In many ways
the symptoms of this disease overlap with those of Alzheimer's
magnetic resonance imaging (MRI) - a diagnostic
imaging technique that uses magnetic fields and radio waves to
produce detailed images of body structures.
mild cognitive impairment - a condition
associated with impairments in understanding and memory not severe
enough to be diagnosed as dementia, but more pronounced than those
associated with normal aging.
Mini-Mental State Examination - a test used to
assess cognitive skills in people with suspected dementia. The test
examines orientation, memory, and attention, as well as the ability
to name objects, follow verbal and written commands, write a
sentence spontaneously, and copy a complex shape.
multi-infarct dementia - a type of vascular
dementia caused by numerous small strokes in the brain.
myelin - a fatty substance that coats and
insulates nerve cells.
neurofibrillary tangles - bundles of twisted
filaments found within neurons, and a characteristic feature found
in the brains of Alzheimer's patients. These tangles are largely
made up of a protein called tau.
neurotransmitter - a type of chemical, such as
acetylcholine, that transmits signals from one neuron to another.
People with Alzheimer's disease have reduced supplies of
organic brain syndrome - a term that refers to
physical disorders (not psychiatric in origin) that impair mental
Parkinson's dementia - a secondary dementia that
sometimes occurs in people with advanced Parkinson's disease, which
is primarily a movement disorder. Many Parkinson's patients have the
characteristic amyloid plaques and neurofibrillary tangles found in
Alzheimer's disease, but it is not yet clear if the diseases are
Pick's disease - a type of frontotemporal
dementia where certain nerve cells become abnormal and swollen
before they die. The brains of people with Pick's disease have
abnormal structures, called Pick bodies, inside the neurons. The
symptoms are very similar to those of Alzheimer's diease.
plaques - unusual clumps of material found
between the tissues of the brain in Alzheimer's disease. See
also amyloid plaques.
post-traumatic dementia - a dementia brought on
by a single traumatic brain injury. It is much like dementia
pugilistica, but usually also includes long-term memory
presenilin 1 and 2 - proteins produced by genes
that influence susceptibility to early-onset Alzheimer's
primary dementia - a dementia, such as
Alzheimer's disease, that is not the result of another disease.
primary progressive aphasia - a type of
frontotemporal dementia resulting in deficits in language functions.
Many, but not all, people with this type of aphasia eventually
develop symptoms of dementia.
progressive dementia - a dementia that gets
worse over time, gradually interfering with more and more cognitive
secondary dementia - a dementia that occurs as a
consequence of another disease or an injury.
senile dementia - an outdated term that reflects
the formerly widespread belief that dementia was a normal part of
aging. The word senile is derived from a Latin term that
means, roughly, "old age. "
subcortical dementia - dementia that affects
parts of the brain below the outer brain layer, or cortex.
substance-induced persisting dementia - dementia
caused by abuse of substances such as alcohol and recreational drugs
that persists even after the substance abuse has ended.
tau protein - a protein that helps the
functioning of microtubules, which are part of the cell's structural
support and help to deliver substances throughout the cell. In
Alzheimer's disease, tau is changed in a way that causes it
to twist into pairs of helical filaments that collect into
transmissible spongiform encephalopathies - part
of a family of human and animal diseases in which brains become
filled with holes resembling sponges when examined under a
microscope. CJD is the most common of the known transmissible
vascular dementia - a type of dementia caused by
brain damage from cerebrovascular or cardiovascular problems -
usually strokes. It accounts for up to 20 percent of all
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The National Institute of Neurological Disorders and Stroke
It is a
component of the National Institutes of Health, is the leading
federal supporter of research on brain and nervous system. The
Institute also sponsors an active public information program and
can answer questions about research related to the dementias.
For information on other neurological disorders or research
programs funded by the National Institute of Neurological Disorders
and Stroke, contact the Institute's Brain Resources and Information
Network (BRAIN) at:
Information is also available from the following Federal
Alzheimer's Disease Education and Referral Center
National Institute of Mental Health (NIMH)
Alzheimer's Foundation of America
National Organization for Rare Disorders (NORD)
Family Caregiver Alliance
Association for Frontotemporal Dementias (AFTD)
C-Mac Informational Services/Caregiver News [For Alzheimer's
Type Dementia Caregivers]
National Family Caregivers Association
Well Spouse Foundation
National Respite Network and Resource Center
American Health Assistance Foundation
National Hospice and Palliative Care Organization /Natl.
Institute for the Study of Aging
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