A mother and daughter living with Alzheimers.

What is Alzheimer's disease (AD)?

Alzheimer’s disease (AD) is a progressive, fatal brain disease.

How common is Alzheimer’s disease (AD)?

One in 10 people older than 65 and nearly half of people older than 85 have Alzheimer’s disease. AD can affect people in their 40s. The percentage of people who have AD rises every decade beyond the age of 60. According to the Alzheimer's Association, with the aging of the population, and without successful treatment, there will be 16 million Americans and 106 million people worldwide with AD by 2050.

While AD is the most common cause of dementia (accounting for 62 percent to 70 percent of cases), there are other causes. These include:

How do changes in the brain happen because of Alzheimer’s disease?

Key changes in the brain in AD include:

  • Brain shrinkage. This is called atrophy
  • The loss of nerve cells
  • The presence of neuritic amyloid plaques (protein deposits that collect between nerve cells, or neurons)
  • The presence of neurofibrillary tangles (twisted fibers in the nerve cells, thought to contribute to cell breakdown)
  • Brain inflammation (swelling)

What causes Alzheimer’s disease (AD)?

Alzheimer’s disease is caused by the abnormal build-up of proteins in the brain. The build-up of the proteins — amyloid protein and tau protein — leads to cell death.

What are the symptoms of Alzheimer’s disease (AD)?

Alzheimer’s disease affects the areas of the brain that are essential for thinking, memory, and behavior. Symptoms of the disease include:

  • Memory loss
  • Tendency to misplace things
  • Trouble performing familiar tasks
  • Changes in personality and behavior
  • Poor judgment
  • Problems with language
  • Impaired visuospatial skills (trouble understanding spatial relationships of objects)