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Definition

Dementia is a loss of brain function that occurs with certain diseases. Alzheimer disease (AD) is the most common form of dementia. It affects memory, thinking, and behavior.

Dementia may also be referred to as major neurocognitive disorder.

Causes

The exact cause of Alzheimer disease is not known. Research shows that certain changes in the brain are associated with Alzheimer disease. This leads to structures called neuritic plaques and neurofibrillary tangles. Most experts believe that this is the cause of Alzheimer disease but why this happens to some people is not known.

You are more likely to develop Alzheimer disease if you:

• Are older -- Developing Alzheimer disease is not a part of normal aging.
• Have a close relative, such as a brother, sister, or parent with Alzheimer disease.
• Have certain genes linked to Alzheimer disease.

The following may also increase the risk:

• Being female
• Having heart and blood vessel problems due to high cholesterol
• History of head trauma

There are two types of Alzheimer disease:

• Early onset Alzheimer disease -- Symptoms appear before age 60. This type is much less common than late onset. It tends to get worse quickly. Early onset disease can run in families. Several genes have been identified.
• Late onset Alzheimer disease -- This is the most common type. It occurs in people age 60 and older. It may run in some families, but the role of genes is less clear.

Symptoms

Alzheimer disease symptoms include difficulty with many areas of mental function, including:

• Emotional behavior or personality
• Language
• Memory
• Perception
• Thinking and judgment (cognitive skills)

Alzheimer disease usually first appears as forgetfulness.

Mild cognitive impairment (MCI) is a condition in which a person has more memory and thinking problems than other people their age. People with MCI have mild problems with thinking and memory that do not interfere with daily activities. They are often aware of the forgetfulness. Not everyone with MCI develops Alzheimer disease.

Symptoms of MCI include:

• Difficulty doing more than one task at a time
• Difficulty solving problems or making decisions
• Forgetting names of familiar people, recent events, or conversations
• Taking longer to do more difficult mental activities

Early symptoms of Alzheimer disease can include:

• Difficulty performing tasks that take some thought, but used to come easily, such as balancing a checkbook, playing complex games (bridge), and learning new information or routines
• Getting lost on familiar routes
• Language problems, such as trouble remembering the names of familiar objects
• Losing interest in things previously enjoyed and being in a flat mood
• Misplacing items
• Personality changes and loss of social skills
• Mood changes leading to aggressive behavior
• Poor performance of job duties

As Alzheimer disease becomes worse, symptoms are more obvious and interfere with the ability to take care of oneself. Symptoms may include:

• Change in sleep patterns, often waking up at night
• Delusions, depression, and agitation
• Difficulty doing basic tasks, such as preparing meals, choosing proper clothing, and driving
• Difficulty reading or writing
• Forgetting details about current events
• Forgetting events in one's life history and losing self-awareness
• Hallucinations, arguments, striking out, and violent behavior
• Poor judgment and loss of ability to recognize danger
• Using the wrong word, mispronouncing words, or speaking in confusing sentences
• Withdrawing from social contact

People with severe Alzheimer disease can no longer:

• Recognize family members
• Perform basic activities of daily living, such as eating, dressing, and bathing
• Understand language

Other symptoms that may occur with Alzheimer disease:

• Problems controlling bowel movements or urine
• Swallowing problems

Exams and Tests

A diagnosis of Alzheimer disease is made when certain symptoms are present, and by making sure other causes of dementia are not present.

A skilled health care provider can often diagnose Alzheimer disease with the following steps:

• Performing a complete physical exam, including a nervous system exam.
• Asking about the person's medical history and symptoms.
• Mental function tests (mental status examination).
• Neuropsychological testing.
• PET scan and lumbar puncture (spinal tap) are sometimes needed to confirm Alzheimer disease.

Tests may be done to rule out other possible causes of dementia, including:

• Anemia
• Brain tumor
• Long-term (chronic) infection
• Intoxication from medicines
• Severe depression
• Increased fluid on the brain (normal pressure hydrocephalus)
• Stroke
• Thyroid disease
• Vitamin deficiency

CT or MRI of the brain may be done to look for other causes of dementia, such as a brain tumor or stroke.

The only way to know for certain that someone has Alzheimer disease is to examine a sample of their brain tissue after death.

Treatment

There is no cure for Alzheimer disease. The goals of treatment are:

• Slow the progression of the disease (although this is difficult to do)
• Manage symptoms, such as behavior problems, confusion, and sleep problems
• Change the home environment to make daily activities easier
• Support family members and other caregivers

Medicines are used to:

• Slow the rate at which symptoms worsen, though the benefit from using these medicines may be small
• Lower the amount of beta amyloid protein in the brain
• Control problems with behavior, such as loss of judgment or confusion

Before using these medicines, ask your provider:

• What are the side effects? Is the medicine worth the risk?
• When is the best time, if any, to use these medicines?
• Do medicines for other health problems need to be changed or stopped?

Someone with Alzheimer disease will need support in the home as the disease gets worse. Family members or other caregivers can help by helping the person cope with memory loss and behavior and sleep problems. It is important to make sure the home of a person who has Alzheimer disease is safe for them.

Support Groups

Having Alzheimer disease or caring for a person with the condition may be a challenge. You can ease the stress of illness by seeking support through Alzheimer disease resources. Sharing with others who have common experiences and problems can help you not feel alone.

Outlook (Prognosis)

How quickly Alzheimer disease gets worse is different for each person. If Alzheimer disease develops quickly, it is more likely to worsen quickly.

People with Alzheimer disease often die earlier than normal, although a person may live anywhere from 3 to 20 years after diagnosis.

Families will likely need to plan for their loved one's future care.

The final phase of the disease may last from a few months to several years. During that time, the person becomes totally disabled. Death usually occurs from an infection or organ failure.

When to Contact a Medical Professional

Contact your provider if:

• Alzheimer disease symptoms develop or a person has a sudden change in mental status
• The condition of a person with Alzheimer disease gets worse
• You are unable to care for a person with Alzheimer disease at home

Prevention

Although there is no proven way to prevent Alzheimer disease, there are some measures that may help prevent or slow the onset of Alzheimer disease:

• Stay on a low-fat diet and eat foods high in omega-3 fatty acids.
• Get plenty of exercise.
• Stay mentally and socially active.
• Wear a helmet during risky activities to prevent brain injury.

References

Alzheimer's Association website. First practice guidelines for clinical evaluation of Alzheimer's disease and other dementias for primary and specialty care. [press release] July 22, 2018. aaic.alz.org/releases_2018/AAIC18-Sun-clinical-practice-guidelines.asp. Accessed May 8, 2024.

Budson AE, Solomon PR. Alzheimer's disease. In: Budson AE, Solomon PR, eds. Memory Loss, Alzheimer's Disease, and Dementia. 3rd ed. Philadelphia, PA: Elsevier; 2022:chap 4.

Knopman DS. Cognitive impairment and dementia. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 371.

Peterson RC, Graff-Radford J. Alzheimer disease and other dementias. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 95.

Wilamowska K, Knoefel J. Alzheimer's disease. In: Kellerman RD, Rakel DP, Heidelbaugh JJ, Lee EM, eds. Conn's Current Therapy 2024. Philadelphia, PA: Elsevier 2024:741-748.

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