Alzheimer disease (AD) is a brain illness that usually occurs in older adults. Typical AD is very common in people older than 80 years of age. It is unusual for typical AD to occur before age 65. It's the most common cause of dementia and is a progressive disease. This means it gets worse over time.

Alzheimer disease causes a series of changes to the nerves of the brain. Some nerves form into clumps and tangles and lose some of their connections to other nerves.

Doctors don't fully understand what causes Alzheimer disease. But they think these may be some of the causes:

• Age and family history
• Certain genes
• Abnormal protein deposits in the brain
• Environmental factors
• Problems with a person's immune system
• Possibly infections
• Reduced blood flow to the brain
• Repeated head injuries (such as from sports)

The disease causes changes in behavior and thinking known as dementia. The symptoms include:

• Memory loss
• Confusion
• Restlessness
• Personality and behavior changes
• Problems with judgment
• Problems communicating with others
• Inability to follow directions
• Lack of emotion
• Aggression, hallucinations, and delusions

No single test is able to diagnose Alzheimer disease. Instead, doctors use a series of tests to rule out other health conditions. The tests may include:

• A complete health history. This may include questions about overall health and past health problems. The doctor may ask how well the person can do daily tasks. The doctor may ask family or close friends about any changes in behavior or personality.
• Mental status test. This is a test of memory, problem-solving, attention, counting, and language.
• Standard medical tests. These may include blood and urine tests to find possible causes for the problem.
• Brain imaging tests. CT, MRI, or positron emission tomography (PET) may be used to rule out other causes of the problem.
• Neuropsychological testing. These are more advanced tests of memory and other brain functions that can determine the extent of brain dysfunction.

Alzheimer disease has no cure. Instead, doctors can help ease some symptoms. This can make a person with Alzheimer disease more comfortable. Treatment can also make it easier for their caregivers to take care of them.

Some medicines may help slow the decline of a person's memory, thinking, and language skills. They may help with problems of behavior, such as aggression. They can reduce hallucinations and delusions. These medicines can work for some but not all people. And they may help for only a limited time. Medicines include:

• Donepezil
• Galantamine
• Rivastigmine
• Memantine
• Lecanemab-irmb

In some cases, behavior problems can be caused by a medicine's side effects. Talk with the person's doctor about all medicines they are taking. Never increase or decrease a person's medicines unless you talk with the doctor. Never share medicines or use someone else's prescriptions. If you have trouble paying for the prescriptions, talk to the doctor or the pharmacist about how to get help with this.

For a person with Alzheimer disease, it's important to stay healthy. Good nutrition and physical and social activity are vital. A calm and well-structured environment will help. Make sure to keep up with health care appointments and manage other health conditions, such as diabetes and high blood pressure. Some people benefit from having a nutritionist help to prevent weight loss.

A person with Alzheimer disease will need more caregiving over time. Talk with your doctor about caregiving resources.

• Alzheimer's Association, 800-272-3900
• National Institute on Aging, 800-222-2225
• Alzheimer's Foundation of America, 866-232-8484