Last Updated: April 2, 2013
Dementia is a brain disorder that seriously affects a person's
ability to carry out daily activities. The most common form of
dementia among older people is Alzheimer's disease (AD), which
initially involves the parts of the brain that control thought,
memory, and language. Although scientists are learning more every
day, right now they still do not know what causes AD, and there is
Scientists think that as many as 4.5 million Americans suffer
from Alzheimer's disease. The disease usually begins after age 60,
and risk goes up with age. While younger people also may get AD, it
is much less common. About 5% of men and women ages 65 to 74 have
AD, and nearly half of those age 85 and older may have the disease.
It is important to note, however, that AD is not a normal part of
Alzheimer's disease is named after Dr. Alois Alzheimer, a German
doctor. In 1906, Dr. Alzheimer noticed changes in the brain tissue
of a woman who had died of an unusual mental illness. He found
abnormal clumps (now called amyloid plaques) and tangled bundles of
fibers (now called neurofibrillary tangles). Today, these plaques
and tangles in the brain are considered signs of AD.
Scientists also have found other brain changes in people with
AD. Nerve cells die in areas of the brain that are vital to memory
and other mental abilities, and connections between nerve cells are
disrupted. There also are lower levels of some of the chemicals in
the brain that carry messages back and forth between nerve cells.
AD may impair thinking and memory by disrupting these messages.
What Causes Alzheimer's Disease?
Scientists do not yet fully understand what causes AD. There
probably is not one single cause, but several factors that affect
each person differently. Age is the most important known risk
factor for AD. The number of people with the disease doubles every
5 years beyond age 65.
Family history is another risk factor. Scientists believe that
genetics may play a role in many AD cases. For example, early-onset
familial AD, a rare form of AD that usually occurs between the ages
of 30 and 60, is inherited. The more common form of AD is known as
late-onset. It occurs later in life, and no obvious inheritance
pattern is seen in most families. However, several risk factor
genes may interact with each other and with non-genetic factors to
cause the disease. The only risk factor gene identified so far for
late-onset AD is a gene that makes one form of a protein called
apolipoprotein E (ApoE). Everyone has ApoE, which helps carry
cholesterol in the blood. Only about 15 percent of people have the
form that increases the risk of AD. It is likely that other genes
also may increase the risk of AD or protect against AD, but they
remain to be discovered.
Scientists still need to learn a lot more about what causes AD.
In addition to genetics and ApoE, they are studying education,
diet, and environment to learn what role they might play in the
development of this disease. Scientists are finding increasing
evidence that some of the risk factors for heart disease and
stroke, such as high blood pressure, high cholesterol, and low
levels of the vitamin folate, may also increase the risk of AD.
Evidence for physical, mental, and social activities as protective
factors against AD is also increasing.
What Are the Symptoms of Alzheimer's Disease?
Alzheimer's disease begins slowly. At first, the only symptom
may be mild forgetfulness, which can be confused with age-related
memory change. Most people with mild forgetfulness do not have AD.
In the early stage of AD, people may have trouble remembering
recent events, activities, or the names of familiar people or
things. They may not be able to solve simple math problems. Such
difficulties may be a bother, but usually they are not serious
enough to cause alarm.
However, as the disease goes on,
symptoms are more easily noticed and become serious enough to
cause people with AD or their family members to seek medical help.
Forgetfulness begins to interfere with daily activities. People in
the middle stages of AD may forget how to do simple tasks like
brushing their teeth or combing their hair. They can no longer
think clearly. They can fail to recognize familiar people and
places. They begin to have problems speaking, understanding,
reading, or writing. Later on, people with AD may become anxious or
aggressive, or wander away from home. Eventually, patients need
How is Alzheimer's Disease Diagnosed?
An early, accurate diagnosis of AD helps patients and their
families plan for the future. It gives them time to discuss care
while the patient can still take part in making decisions. Early
diagnosis will also offer the best chance to treat the symptoms of
Today, the only definite way to diagnose AD is to find out
whether there are plaques and tangles in brain tissue. To look at
brain tissue, however, doctors usually must wait until they do an
autopsy, which is an examination of the body done after a person
dies. Therefore, doctors can only make a diagnosis of "possible" or
"probable" AD while the person is still alive.
At specialized centers, doctors can diagnose AD correctly up to
90 percent of the time. Doctors use several tools to diagnose
"probable" AD, including:
- questions about the person's general health, past medical
problems, and ability to carry out daily activities,
- tests of memory, problem solving, attention, counting, and
- medical tests-such as tests of blood, urine, or spinal fluid,
- brain scans.
Sometimes these test results help the doctor find other possible
causes of the person's symptoms. For example, thyroid problems,
drug reactions, depression, brain tumors, and blood vessel disease
in the brain can cause AD-like symptoms. Some of these other
conditions can be treated successfully.
How is Alzheimer's Disease Treated?
Alzheimer's disease is a slow disease, starting with mild memory
problems and ending with severe brain damage. The course the
disease takes and how fast changes occur vary from person to
person. On average, AD patients live from 8 to 10 years after they
are diagnosed, though some people may
live with Alzheimer's for as many as 20 years.
No treatment can stop AD. However, for some people in the early
and middle stages of the disease, the drugs tacrine (Cognex),
donepezil (Aricept), rivastigmine (Exelon), or galantamine
(Razadyne, previously known as Reminyl) may help prevent some
symptoms from becoming worse for a limited time. Another drug,
memantine (Namenda), has been approved to treat moderate to severe
AD, although it also is limited in its effects. Also, some
medicines may help control behavioral symptoms of AD such as
sleeplessness, agitation, wandering, anxiety, and depression.
Treating these symptoms often makes patients more comfortable and
makes their care easier for caregivers.
New Areas of Research
Mild Cognitive Impairment.During the past several years,
scientists have focused on a type of memory change called mild
cognitive impairment (MCI), which is different from both
Alzheimer's disease and normal age-related memory change. People
with MCI have ongoing
memory problems, but they do not have other losses such as
confusion, attention problems, and difficulty with language. The
NIA-funded Memory Impairment Study compared donepezil (Aricept),
vitamin E, or placebo in participants with MCI to see whether the
drugs might delay or prevent progression to AD. The study found
that the group with MCI taking the drug donepezil was at reduced
risk of progressing to AD for the first 18 months of a 3-year study
when compared with their counterparts on placebo. The reduced risk
of progressing from MCI to a diagnosis of AD among participants on
donepezil disappeared after 18 months, and by the end of the study,
the probability of progressing to AD was the same in the two
groups. Vitamin E had no effect at any time point in the study when
compared with placebo.
Neuroimaging.Scientists are finding that damage to parts of the
brain involved in memory, such as the hippocampus, can sometimes be
seen on brain scans before symptoms of the disease occur.
AD Genetics.The NIA is sponsoring the AD Genetics Study to learn
more about risk factor genes for late onset AD.
Inflammation.There is evidence that inflammation in the brain
may contribute to AD damage. Some studies have suggested that drugs
such as nonsteroidal anti-inflammatory drugs (NSAIDs) might help
slow the progression of AD, but clinical trials thus far have not
demonstrated a benefit from these drugs. A clinical trial studying
two of these drugs, rofecoxib (Vioxx) and naproxen (Aleve) showed
that they did not delay the progression of AD in people who already
have the disease. Another trial, testing whether the NSAIDs
celecoxib (Celebrex) and naproxen could prevent AD in healthy older
people at risk of the disease, has been suspended. However,
investigators are continuing to follow the participants and are
examining data regarding possible cardiovascular risk. Researchers
are continuing to look for ways to test how other anti-inflammatory
drugs might affect the development or progression of AD.
Antioxidants.Several years ago, a clinical trial showed that
vitamin E slowed the progress of some consequences of AD by about 7
months. Additional studies are investigating whether
antioxidants-vitamins E and C-can slow AD. Another clinical trial
is examining whether vitamin E and/or selenium supplements can
prevent AD or cognitive decline, and additional studies on other
antioxidants are ongoing or being planned.
Ginkgo biloba.Early studies suggested that extracts from the
leaves of the ginkgo biloba tree may be of some help in treating AD
symptoms. There is no evidence yet that ginkgo biloba will cure or
prevent AD, but scientists now are trying to find out in a clinical
trial whether ginkgo biloba can delay cognitive decline or prevent
dementia in older people.
Estrogen.Some studies have suggested that estrogen used by women
to treat the symptoms of menopause also protects the brain. Experts
also wondered whether using estrogen could reduce the risk of AD or
slow the disease. Clinical trials to test estrogen, however, have
not shown that estrogen can slow the progression of already
diagnosed AD. And one study found that women over the age of 65 who
used estrogen with a progestin were at greater risk of dementia,
including AD, and that older women using only estrogen could also
increase their chance of developing dementia.
Scientists believe that more research is needed to find out if
estrogen may play some role in AD. They would like to know whether
starting estrogen therapy around the time of menopause, rather than
at age 65 or older, will protect memory or prevent AD.
Advancing Our Understanding
Scientists have come a long way in their understanding of
Alzheimer's disease. Findings from years of research have begun to
clarify differences between normal age-related memory changes, MCI,
and AD. Scientists also have made great progress in defining the
changes that take place in the AD brain, which allows them to
pinpoint possible targets for treatment. These advances are
the foundation for the NIH Alzheimer's Disease Prevention
Initiative, which is designed to:
- understand why AD occurs and who is at greatest risk of
- improve the accuracy of diagnosis and the ability to identify
those at risk;
- discover, develop, and test new treatments;
- discover treatments for behavioral problems in patients with
Is There Help for Caregivers?
Most often, spouses and other family members provide the
day-to-day care for people with Alzheimer's disease. As the disease
gets worse, people often need more and more care. This can be hard
for caregivers and can affect their physical and mental health,
family life, job, and finances.
The Alzheimer's Association has chapters nationwide that provide
educational programs and support groups for caregivers and family
members of people with AD. Contact information for the Alzheimer's
Association is listed below.
For More Alzheimer's Disease Information
To learn about support groups, services, research centers,
getting involved in studies, and publications about AD, contact the
Alzheimer's Disease Education and Referral (ADEAR)
P.O. Box 8250
Silver Spring, MD 20907-8250
225 N. Michigan Avenue, Suite 1700
Chicago, IL 60611-7633
Source: National Institute on Aging, www.nia.nih.gov (Original
title:Alzheimer's Disease Fact Sheet)