Many but not all people with Down syndrome develop Alzheimer’s disease when they get older.

People with Down syndrome are born with an extra copy of chromosome 21, which carries a gene that produces a specific protein called amyloid precursor protein (APP). Too much APP protein leads to a buildup of protein clumps called beta-amyloid plaques in the brain. The presence of beta-amyloid plaques is one of the hallmarks of Alzheimer’s disease.

Many but not all people with Down syndrome develop Alzheimer’s disease when they get older.

By age 40, most people with Down syndrome have these plaques, along with other protein deposits, called tau tangles, which cause problems with how brain cells function and increase the risk of developing Alzheimer’s symptoms. Estimates suggest that 50% or more of people with Down syndrome will develop dementia due to Alzheimer’s disease as they age.

This type of Alzheimer’s in people with Down syndrome is not passed down genetically from a parent to a child.

Down Syndrome and Alzheimer’s Research

Scientists are working hard to understand why some people with Down syndrome develop dementia while others do not. They want to know how Alzheimer’s disease begins and progresses so they can develop drugs or other treatments that can stop, delay, or even prevent the disease process. They are also hopeful that research on Alzheimer’s and Down syndrome will not only help those with both conditions, but also may lead to effective treatments for all people with Alzheimer’s. Research in this area includes:

• Basic studies to improve understanding of the genetic and biological causes of brain abnormalities that lead to Alzheimer’s
• Observational research to measure cognitive changes in people over time
• Studies of biomarkers (biological signs of disease), brain scans, and other tests that may help diagnose Alzheimer’s — even before symptoms appear — and show brain changes as people with Down syndrome age
• Clinical trials to test treatments for dementia in adults with Down syndrome

The Alzheimer’s Biomarkers Consortium – Down Syndrome (ABC-DS) is a National Institutes of Health (NIH)-funded research initiative to find biomarkers that indicate Alzheimer’s disease is developing or progressing, and to track the Alzheimer’s process in people with Down syndrome.