Alzheimer’s disease is an 

irreversible, progressive brain 

disease that slowly destroys 

memory and thinking skills, and 

eventually even the ability to carry 

out the simplest tasks. In most 

people with Alzheimer’s, symptoms 

first appear after age 60. Estimates 

vary, but experts suggest that as 

many as 5.1 million Americans 

may have Alzheimer’s disease.

Alzheimer’s disease is the most 

common cause of dementia among 

older people. Dementia is the loss of

cognitive functioning—thinking, 

remembering, and reasoning—and 

behavioral abilities, to such an extent

that it interferes with a person’s daily

life and activities. Dementia ranges

in severity from the mildest stage, 

when it is just beginning to affect

a person’s functioning, to the most 

severe stage, when the person must

depend completely on others for basic

activities of daily living.

Alzheimer’s disease is named 

after Dr. Alois Alzheimer. In 1906, 

Dr. Alzheimer noticed changes in

the brain tissue of a woman who

had died of an unusual mental 

illness. Her symptoms included 

memory loss, language problems, 

and unpredictable behavior. After 

she died, he examined her brain 

and found many abnormal clumps 

(now called amyloid plaques) and 

tangled bundles of fibers (now 

called neurofibrillary tangles). 

Plaques and tangles in the brain 

are two of the main features of 

Alzheimer’s disease. The third is 

the loss of connections between 

nerve cells (neurons) in the brain. 

Changes in the Brain in 

Alzheimer’s Disease

Although we still don’t know how 

the Alzheimer’s disease process 

begins, it seems likely that damage 

to the brain starts a decade or more 

before problems become evident. 

During the preclinical stage of 

Alzheimer’s disease, people are free 

of symptoms but toxic changes are 

taking place in the brain. Abnormal 

deposits of proteins form amyloid 

plaques and tau tangles throughout 

the brain, and once-healthy neurons 

begin to work less efficiently. Over 

Alzheimer’s Disease Education & Referral (ADEAR) Center

A Service of the National Institute on Aging

National Institutes of Health

U.S. Department of Health and Human Services

FACT SHEET

Alzheimer’s Disease 
time, neurons lose their ability to 

function and communicate with 

each other, and eventually they die. 

Before long, the damage spreads 

to a nearby structure in the brain 

called the hippocampus, which is 

essential in forming memories. 

As more neurons die, affected 

brain regions begin to shrink. By 

the final stage of Alzheimer’s, 

damage is widespread, and brain 

tissue has shrunk significantly. 

Very Early Signs and Symptoms 

Memory problems are typically 

one of the first warning signs of 

cognitive loss, possibly due to the 

development of Alzheimer’s disease. 

Some people with memory problems 

have a condition called amnestic 

mild cognitive impairment (MCI). 

People with this condition have more 

memory problems than normal for 

people their age, but their symptoms

are not as severe as those seen in 

people with Alzheimer’s disease. 

Other recent studies have found 

links between some movement 

difficulties and MCI. Researchers 

also have seen links between MCI 

and some problems with the sense 

of smell. The ability of people with 

MCI to perform normal daily activities is not significantly impaired. 

However, more older people with 

MCI, compared with those without 

MCI, go on to develop Alzheimer’s. 

A decline in other aspects of 

cognition, such as word-finding, 

As Alzheimer’s disease progresses,

neurofibrillary tangles spread throughout 

the brain (shown in blue). Plaques also 

spread throughout the brain, starting in the 

neocortex. By the final stage, damage is 

widespread, and brain tissue has shrunk 

significantly. 

vision/spatial issues, and impaired 

reasoning or judgment, may also 

signal the very early stages of 

Alzheimer’s disease. Scientists 

are looking to see whether brain 

imaging and biomarker studies, 

for example, of people with MCI 

and those with a family history 

of Alzheimer’s, can detect early 

changes in the brain like those 

seen in Alzheimer’s. Initial studies 

indicate that early detection using

biomarkers and imaging may be 

possible, but findings will need to be

confirmed by other studies before

these techniques can be used to 

help with diagnosis in everyday 

medical practice. 

Very Early

Alzheimer’s

Mild to 

Moderate

Alzheimer’s

Severe

Alzheimer’s

2
These and other studies offer hope 

that someday we may have tools that 

could help detect Alzheimer’s early, 

track the course of the disease, and 

monitor response to treatments. 

Mild Alzheimer’s Disease

As Alzheimer’s disease progresses, 

memory loss worsens, and changes in 

other cognitive abilities are evident. 

Problems can include, for example, 

getting lost, trouble handling money 

and paying bills, repeating questions, 

taking longer to complete normal 

daily tasks, using poor judgment, and 

having some mood and personality 

changes. People often are diagnosed 

in this stage. 

Moderate Alzheimer’s Disease

In this stage, damage occurs in areas 

of the brain that control language, 

reasoning, sensory processing, and 

conscious thought. Memory loss and 

confusion grow worse, and people 

begin to have problems recognizing 

family and friends. They may be unable to learn new things, carry out 

tasks that involve multiple steps 

(such as getting dressed), or cope 

with new situations. They may have 

hallucinations, delusions, and paranoia, and may behave impulsively. 

Severe Alzheimer’s Disease 

By the final stage, plaques and tangles

have spread throughout the brain, and

brain tissue has shrunk significantly.

People with severe Alzheimer’s cannot

communicate and are completely 

dependent on others for their care. 

Near the end, the person may be in 

bed most or all of the time as the 

body shuts down. 

What Causes Alzheimer’s

Scientists don’t yet fully understand 

what causes Alzheimer’s disease, but

it has become increasingly clear that 

it develops because of a complex series

of events that take place in the brain 

over a long period of time. It is likely 

that the causes include some mix 

of genetic, environmental, and lifestyle factors. Because people differ in 

their genetic make-up and lifestyle, 

the importance of any one of these 

factors in increasing or decreasing 

the risk of developing Alzheimer’s 

may differ from person to person.

The Basics of Alzheimer’s

Scientists are conducting studies to 

learn more about plaques, tangles, 

and other features of Alzheimer’s 

disease. They can now visualize betaamyloid associated with plaques by

imaging the brains of living individuals. Scientists are also exploring

the very earliest steps in the disease

process. Findings from these studies

will help them understand the

causes of Alzheimer’s.

One of the great mysteries of 

Alzheimer’s disease is why it largely 

strikes older adults. Research on 

how the brain changes normally 

with age is shedding light on this 

question. For example, scientists are 

learning how age-related changes 

in the brain may harm neurons and 

3
4

contribute to Alzheimer’s damage. 

These age-related changes include 

atrophy (shrinking) of certain parts 

of the brain, inflammation, the 

production of unstable molecules 

called free radicals, and mitochondrial dysfunction (a breakdown of 

energy production within a cell).

Genetics 

Early-onset Alzheimer’s is a rare form 

of the disease. It occurs in people age 

30 to 60 and represents less than 5 percent of all people who have Alzheimer’s 

disease. Most cases of early-onset 

Alzheimer’s are familial Alzheimer’s 

disease, caused by changes in one 

of three known genes inherited from 

a parent.

Most people with Alzheimer’s disease 

have “late-onset” Alzheimer’s, which 

usually develops after age 60. Many 

studies have linked the apolipoprotein E 

(APOE) gene to late-onset Alzheimer’s. 

This gene has several forms. 

One of them, APOE ε4, seems to 

increase a person’s risk of getting 

the disease. However, carrying the 

APOE ε4 form of the gene does not 

necessarily mean that a person will 

develop Alzheimer’s disease, and 

people carrying no APOE ε4 can also 

develop the disease. 

Most experts believe that additional

genes may influence the development

of late-onset Alzheimer’s. Scientists 

around the world are searching for 

these genes, and have identified a 

number of common genes in addition 

to APOE ε4 that may increase a person’s risk for late-onset Alzheimer’s. 

For more about this area of research, 

see the Alzheimer’s Disease 

Genetics Fact Sheet, available at 

www.nia.nih.gov/Alzheimers.

Environmental/Lifestyle Factors 

Research also suggests that a host 

of factors beyond basic genetics may 

play a role in the development and 

course of Alzheimer’s disease. There 

is a great deal of interest, for example, 

in associations between cognitive 

decline and vascular and metabolic 

conditions such as heart disease, 

stroke, high blood pressure, diabetes, 

and obesity. Understanding these 

relationships and testing them in 

clinical trials will help us understand 

whether reducing risk factors for 

these conditions may help with

Alzheimer’s as well. 

Further, a nutritious diet, physical

activity, social engagement, and mentally stimulating pursuits can all help 

people stay healthy as they age. New 

research suggests the possibility that 

these and other factors also might help

to reduce the risk of cognitive decline

and Alzheimer’s disease. Clinical trials 

of specific interventions are underway 

to test some of these possibilities. 

4
5

Diagnosing Alzheimer’s

Disease

Alzheimer’s disease can be definitively 

diagnosed only after death, by linking

clinical measures with an examination

of brain tissue and pathology in an 

autopsy. But doctors now have several 

methods and tools to help them determine fairly accurately whether a person

who is having memory problems has 

“possible Alzheimer’s dementia” (dementia may be due to another cause) or 

“probable Alzheimer’s dementia” (no 

other cause for dementia can be found).

To diagnose Alzheimer’s, doctors may:

n Ask questions about overall health,

past medical problems, ability to 

carry out daily activities, and changes

in behavior and personality 

n Conduct tests of memory, problem

solving, attention, counting, and 

language 

n Carry out standard medical tests,

such as blood and urine tests, to

identify other possible causes of

the problem 

n Perform brain scans, such as 

computed tomography (CT) or 

magnetic resonance imaging (MRI), 

to distinguish Alzheimer’s from 

other possible causes for symptoms, 

like stroke or tumor

These tests may be repeated to give

doctors information about how the person’s memory is changing over time. 

Early, accurate diagnosis is beneficial

for several reasons. It can tell people

whether their symptoms are from

Alzheimer’s or another cause, such 

as stroke, tumor, Parkinson’s disease, 

sleep disturbances, side effects of medications, or other conditions that may 

be treatable and possibly reversible.

Beginning treatment early on in the

disease process can help preserve 

function for some time, even though

the underlying disease process cannot 

be changed. Having an early diagnosis 

also helps families plan for the future, 

make living arrangements, take care 

of financial and legal matters, and 

develop support networks. 

In addition, an early diagnosis can 

provide greater opportunities for 

people to get involved in clinical trials.

In a typical clinical trial, scientists 

test a drug or treatment to see if that

intervention is effective and for whom

it would work best. (See the box for

more information.)

Treating Alzheimer’s Disease

Alzheimer’s disease is complex, and it

is unlikely that any one intervention 

will be found to delay, prevent, or cure 

it. That’s why current approaches in 

treatment and research focus on several 

different aspects, including helping
6

6

people maintain mental function, 

managing behavioral symptoms, and 

slowing or delaying the symptoms 

of disease.

Maintaining Mental Function 

Four medications are approved by the

U.S. Food and Drug Administration to

treat Alzheimer’s. Donepezil (Aricept®),

rivastigmine (Exelon®), and galantamine (Razadyne®) are used to treat mild 

to moderate Alzheimer’s (donepezil can

be used for severe Alzheimer’s as well).

Memantine (Namenda®) is used to 

treat moderate to severe Alzheimer’s. 

These drugs work by regulating neurotransmitters (the chemicals that 

transmit messages between neurons). 

They may help maintain thinking, 

memory, and speaking skills, and help 

with certain behavioral problems. 

However, these drugs don’t change 

the underlying disease process, are 

effective for some but not all people, 

and may help only for a limited time.

Managing Behavioral Symptoms 

Common behavioral symptoms of 

Alzheimer’s include sleeplessness, 

agitation, wandering, anxiety, anger, 

and depression. Scientists are learning why these symptoms occur and 

are studying new treatments—drug 

and non-drug—to manage them. 

Treating behavioral symptoms often 

makes people with Alzheimer’s

more comfortable and makes 

their care easier for caregivers. 

Participating in 

Clinical Trials

People with Alzheimer’s disease, those 

with MCI, those with a family history of 

Alzheimer’s, and healthy people with no 

memory problems and no family history 

of the disease may be able to take part in 

clinical trials. Participants in clinical trials 

for Alzheimer’s disease help scientists 

learn about the brain in healthy aging as 

well as what happens in Alzheimer’s. 

Results of clinical trials may lead to 

improved prevention and treatment 

approaches. Volunteering to participate 

in clinical trials is one way to help in the 

fight against Alzheimer’s disease.

The National Institute on Aging (NIA), 

part of the National Institutes of Health 

(NIH), leads the Federal Government’s 

research efforts on Alzheimer’s. NIAsupported Alzheimer’s Disease Centers 

located throughout the United States 

conduct many clinical trials and carry out 

a wide range of research, including studies 

of the causes, diagnosis, and management 

of Alzheimer’s. NIA also sponsors the 

Alzheimer’s Disease Cooperative Study 

(ADCS), a consortium of leading 

researchers throughout the U.S. and 

Canada who conduct clinical trials on 

promising Alzheimer’s treatments.

To find out more about Alzheimer’s clinical 

trials, talk to your health care provider or 

contact NIA’s ADEAR Center at 1-800-

438-4380. Or, visit the ADEAR Center 

clinical trials database at www.nia.nih.gov/

Alzheimers/Clinical-Trials. You also can 

sign up for email alerts that let you know 

when new clinical trials are added to the 

database. More information about clinical 

trials is available at www.ClinicalTrials.gov. 

Also see Participating in Alzheimer’s 

Disease Clinical Trials and Studies

at www.nia.nih.gov/Alzheimers. 
7

Slowing, Delaying, or Preventing

Alzheimer’s Disease

Alzheimer’s disease research has developed to a point where scientists can look

beyond treating symptoms to think 

about addressing underlying disease 

processes. In ongoing clinical trials, 

scientists are looking at many possible 

interventions, such as immunization 

therapy, cognitive training, physical 

activity, antioxidants, and the effects of 

cardiovascular and diabetes treatments. 

Supporting Families

and Caregivers

Caring for a person with Alzheimer’s 

disease can have high physical, emotional, and financial costs. The demands 

of day-to-day care, changing family 

roles, and difficult decisions about placement in a care facility can be hard to

handle. Researchers have learned 

much about Alzheimer’s caregiving, 

and studies are helping to develop 

new ways to support caregivers.

Becoming well-informed about the

disease is one important long-term

strategy. Programs that teach families

about the various stages of Alzheimer’s

and about flexible and practical strategies for dealing with difficult caregiving 

situations provide vital help to those 

who care for people with Alzheimer’s.

Developing good coping skills and a 

strong support network of family and 

friends also are important ways that 

caregivers can help themselves handle 

the stresses of caring for a loved one 

with Alzheimer’s disease. For example, 

staying physically active provides 

physical and emotional benefits. 

Some Alzheimer’s caregivers have found 

that participating in a support group is 

a critical lifeline. These support groups 

allow caregivers to find respite, express 

concerns, share experiences, get tips, and

receive emotional comfort. Many organizations, such as those listed in the “For 

More Information” section, sponsor 

in-person and online support groups 

across the country. There are a growing 

number of groups for people in the early 

stage of Alzheimer’s and their families. 

Support networks can be especially 

valuable when caregivers face the difficult decision of whether and when to 

place a loved one in a nursing home or 

assisted living facility. For more information about at-home caregiving, see

Caring for a Person with Alzheimer’s 

Disease: Your Easy-to-Use Guide 

from the National Institute on Aging

at www.nia.nih.gov/Alzheimers. 

Advancing Understanding

Thirty years ago, we knew very little 

about Alzheimer’s disease. Since then,

scientists have made important advances. 

Research supported by NIA and other

organizations has expanded knowledge 

of brain function in healthy older people,

identified ways we might lessen normal 

age-related declines in mental function, 

and deepened our understanding of 

the disease. Many scientists and physicians are now working together to 

untangle the genetic, biological, and 
8

NIH Publication No. 11-6423 8 July 2011

environmental factors that, over many 

years, ultimately result in Alzheimer’s. 

This effort is bringing us closer to 

better managing and, ultimately, 

preventing this devastating disease.

For More Information

To learn about support groups, 

services, research centers, research 

studies, and publications about 

Alzheimer’s disease, contact the 

following resources:

Alzheimer’s Disease Education 

and Referral (ADEAR) Center

P.O. Box 8250

Silver Spring, MD 20907-8250

1-800-438-4380 (toll-free)

www.nia.nih.gov/Alzheimers

The National Institute on Aging’s 

ADEAR Center offers information and

publications for families, caregivers, 

and professionals on diagnosis, treatment, patient care, caregiver needs, longterm care, education and training, and

research related to Alzheimer’s disease.

Staff members answer telephone, email, 

and written requests and make referrals to local and national resources. 

The ADEAR website provides free, 

online publications in English and 

Spanish; email alerts; an Alzheimer’s 

disease clinical trials database; the

Alzheimer’s Disease Library database; 

and more.

Alzheimer’s Association

225 N. Michigan Avenue, Floor 17

Chicago, IL 60601-7633

1-800-272-3900 (toll-free)

1-866-403-3073 (TDD/toll-free)

www.alz.org

Alzheimer’s Foundation

of America

322 Eighth Avenue, 7th Floor

New York, NY 10001

1-866-AFA-8484 

(1-866-232-8484; toll-free)

www.alzfdn.org 

Eldercare Locator

1-800-677-1116 (toll-free)

www.eldercare.gov

Family Caregiver Alliance

180 Montgomery Street, Suite 900

San Francisco, CA 94104

1-800-445-8106 (toll-free)

www.caregiver.org

NIHSeniorHealth

www.nihseniorhealth.gov/

alzheimersdisease/toc.html