Understand Alzheimer's Disease in One Minute

By age 85 years and older, between 25 and 50 percent of people will exhibit signs of Alzheimer’s disease. Up to 5.3 million Americans currently have Alzheimer’s disease. By 2050, the number is expected to more than double due to the aging of the population.

Dementia is an umbrella term for a group of cognitive disorders typically marked by memory impairment, difficulty in language, motor activity, object recognition, and disturbance of executive function. Alzheimer's is the most common cause of dementia, accounting for 50 percent to 70 percent of dementia cases.

There are two abnormal structures in the brain associated with Alzheimer’s disease:
  • Amyloid plaques are clumps of protein fragments that accumulate outside of cells.
  • Neurofibrillary tangles are clumps of altered proteins inside cells.

Amyloid Plaques form when protein pieces called beta-amyloid clump together. Beta-amyloid comes from a larger protein found in the fatty membrane surrounding nerve cells. The small clumps may block cell-to-cell signaling at synapses.

Neurofibrillary tangles destroy a vital cell transport system made of proteins. Tangles are insoluble twisted fibers found inside the brain's cells. These tangles consist primarily of a protein called tau, which forms part of a structure called a microtubule. The microtubule helps transport nutrients and other important substances from one part of the nerve cell to another. In Alzheimer's disease, however, the tau protein is abnormal and the microtubule structures collapse.

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