The Link Between Down's Syndrome and Alzheimer's Disease

The reason Alzheimer's disease is more common in people with Down's syndrome is not completely known. Alzheimer's disease is associated with increased production of a compound called amyloid beta in the brain. Amyloid beta accumulates and causes loss of brain cells called neurons. Exactly how neuron loss occurs is not well understood. The higher risk for Alzheimer's disease in people with Down's syndrome may be related to the extra copy of chromosome 21 (which causes Down's syndrome) because it leads to increased production of amyloid beta.

The age when symptoms of Alzheimer's disease actually develop may be related to a person's mental capacity (cognitive reserve) or some anatomic characteristics of the brain. That means people with greater brain weight, more brain cells (neurons), and more education may not have symptoms of Alzheimer's disease as early as people with less cognitive reserve. People with Down's syndrome may develop symptoms of Alzheimer's disease earlier in life than other people because of their increased production of amyloid beta and their smaller cognitive reserve.