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Alzheimer's Disease

Medically reviewed by Last updated on Aug 17, 2021.

What is Alzheimer's Disease?

Harvard Health Publishing

Alzheimer's disease (AD) is a loss of brain functions that worsens over time. It is a form of dementia.

Alzheimer's disease damages the brain's intellectual functions. Short term memory often is affected early. Gradually other intellectual functions deteriorate. Judgment becomes impaired. Most people with advanced AD lose their ability to do normal daily activities.

Alzheimer's usually begins after age 60. Occasionally, it affects younger people.

Scientists are uncertain about what causes the symptoms of AD. Alzheimer's patients develop excessive deposits of two proteins in their brains. Researchers believe that these proteins distort communication between brain cells.

A chemical called acetylcholine may also be involved. It helps transmit messages between brain cells. Levels of acetylcholine begin to drop in patients with AD. This may add to the communication problems between brain cells.

Eventually, brain cells themselves are affected. They begin to shrivel and die.

The following factors may increase your risk of Alzheimer's disease:

  • Age. Risk increases with age.
  • Family history. If members of your family, especially parents or siblings, have or had AD, your risk increases.
  • Genetic factors. Inheriting certain genes increases your risk.


Alzheimer's is a progressive disease.

In the earliest stages of AD:

  • New or recent memories are difficult to recall.
  • It is hard to learn and retain new information.

As the diseases gets a little worse:

Older or more distant memories are gradually lost.

  • Other symptoms may appear, including difficulty:
    • Expressing thoughts as spoken words
    • Carrying out simple instructions
    • Interpreting familiar faces or other well-known objects
  • A person may not be able to:
    • Plan meals
    • Manage money
    • Remember to keep doors locked
    • Remember to take medicines
    • Retain their sense of direction, even in a familiar neighborhood.

On the other hand, a person with early AD usually is able to feed, bathe, dress and groom without help.

Many people with AD develop psychological problems. These may include personality changes, irritability, anxiety or depression.

As AD progresses to its middle and late stages, the affected individual may:

  • Have delusions. These are irrational beliefs, especially about being persecuted or having belongings stolen.
  • Have hallucinations. They may believe that they see, hear, smell, taste, or are being touched by something that isn't really there.
  • Become aggressive.
  • Wander away from home if left alone.


A person with Alzheimer's often doesn't recognize that there is a problem. Usually family members and close friends notice the forgetfulness and changes in behavior.

Rather than trying to convince a person that he or she has a problem, arrange for a doctor's appointment. At least one family member or close friend should accompany the patient.

There is no definitive test for Alzheimer's disease. The doctor will diagnose AD by taking a thorough medical history and performing a physical examination. This will include a neurological examination and a mental status exam.

The doctor will want to know about:

  • Memory lapses
  • Difficulty using language
  • Problems learning and retaining new information
  • Difficulty following directions or handling complex tasks
  • Episodes of poor judgment or unusual or risky behaviors

More of this information is likely to be provided by family members and friends.

The doctor will do a neurological examination to check the brain and nerves. He or she will do a brief mental status examination. This includes visual, writing and memory testing.

The doctor will check for other illnesses that can cause symptoms that resemble Alzheimer's disease. Testing may include blood tests, such as measurements of the levels of vitamin B12 and thyroid hormone. Very low levels of vitamin B12 and a very underactive thyroid can cause problems with thinking and memory. These problems can improve and even go away with treatment.

If the doctor's simple testing of thinking and memory indicate that there may be a problem, more detailed testing of brain function can be done. This is called neuropsychological testing.

In some cases, the doctor may order a brain imaging study. A brain study can rule out other reasons for the symptoms. Brain imaging studies cannot diagnose Alzheimer's with certainty. However, together with the doctor's examination, and the blood and neuropsychological testing, they can help the doctor make a diagnosis.

The doctor may refer you to a specialist to confirm the diagnosis. Specialists include neurologists, geriatricians and geriatric psychiatrists.

Expected Duration

Alzheimer's disease is irreversible. Once the diagnosis is made, mental function usually declines until death.


Staying physically and mentally active may help lower your risk of developing the disease.

In addition, regular physical exercise and a diet that includes fish, olive oil, and plenty of vegetables may delay the onset of symptoms and slow disease progression.


There is no cure for Alzheimer's disease. The goal of treatment is to manage symptoms and slow the progression of the disease.

A class of drugs called cholinesterase inhibitors helps to restore communication between brain cells. These drugs may slow intellectual decline in some people with mild to moderate AD. They work by increasing the brain's levels of acetylcholine.

Memantine works differently. It has been shown to stabilize memory in some people with moderate to severe AD.

Several specialists may be involved in care of the person with Alzheimer's disease, such as neurologists, psychologists, psychiatrists or geriatric doctors. Nurses and social workers play a very important role in care.

Medications may be given to relieve depression and calm agitated behavior.

Here are some easy to implement aspects of care that help ease symptoms:

  • Familiar surroundings, people and routines, because too much change can cause confusion and agitation
  • Bright, active environments to help focus the person's attention and keep him or her oriented to the environment
  • Safe environments so that the person cannot be hurt or get lost if he or she wanders away
  • Physical exercise to improve balance and general good health
  • Appropriate therapies, including music, art and occupational therapy, to provide stimulation and improve control of muscles

The affected person often is unaware of these problems. He or she may even deny that they exist.

Treatment options

The following list of medications are in some way related to or used in the treatment of this condition.

View more treatment options


No medication can cure Alzheimer's disease. But family support and medications may help the person maintain the ability to perform daily activities and relieve behavior problems. These measures may help allow the affected person to remain in his or her home.

External resources

Alzheimer's Association

Alzheimer's Disease & Related Dementias

The Fisher Center for Alzheimer's Research Foundation

When To Call a Professional

Call your doctor whenever you or a family member has any of the following problems:

Serious lapses in memory or judgment Forgets medication Forgets the stove is on Allows strangers into the home Gets lost while driving or walking, especially in a familiar neighborhood Substantial change in personality

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.