How is dementia different from Alzheimer’s disease?
Alzheimer’s is the most common cause of dementia among older adults. Dementia is the loss of cognitive functioning—remembering, communicating and reasoning—and behavioral abilities to such an extent that it interferes with a person’s daily life and activities. Dementia ranges in severity from the mildest stage, when it is just beginning to affect a person’s functioning, to the most severe stage, when the person must depend completely on others for basic activities of daily living. Alzheimer’s disease is characterized by the presence of “plaques” and “tangles” in the brain, which are thought to play an important part in its development and progression.
The major component of these plaques, which accumulate outside of neurons, is a protein called “beta-amyloid.” Beta-amyloid is produced from a larger parent protein called the Amyloid Precursor Protein, or APP. The tangles, on the other hand, develop inside affected neurons and are thought to develop as a result of the presence of beta-amyloid outside the neurons. Both of these, the beta-amyloid plaques and the tangles lead to injury and death of neurons. The disease begins in certain portions of the brain and then slowly spreads. Recent research shows that Alzheimer’s disease-related changes occur in the brain 15-20 years before the onset of dementia symptoms.
What is the link between Alzheimer’s disease and Down syndrome?
Down syndrome is a genetic disorder in which an individual has three copies of the 21st chromosome instead of two. It is the most common genetic cause of learning disabilities in children and is associated with developmental delays, learning difficulties, health issues, and some physical differences. In the past 20 years, the average life expectancy of individuals with Down syndrome has increased dramatically mostly due to improvements in health care and decreased infant mortality. The life expectancy of an individual with Down syndrome is currently in the 60’s. People with Down syndrome are more likely to have certain illnesses and medical conditions, including Alzheimer’s disease.
The gene that drives production of the Amyloid precursor Protein (APP) resides on chromosome 21. Since individuals with Down syndrome have an extra copy of the 21st chromosome, they are more likely to have an over-production of APP. This isn’t completely understood at this time, but one theory is that more APP could mean more beta-amyloid production in the brain. Virtually all individuals with Down syndrome develop the same plaques and tangles in the brain that are seen in Alzheimer’s disease by the time they reach the age of 40 years. Because of this, people with Down syndrome have at least a 70% risk of developing dementia due to Alzheimer’s disease at some point in their life.
Better therapies for Alzheimer’s disease in Down syndrome
Although there are medications that help with symptoms of Alzheimer’s disease, there is currently no cure. Today, there is a worldwide effort underway to find better treatments that may delay the onset of AD or prevent it from developing. More research is needed to understand how the disease develops in people with Down Syndrome and possible treatments to delay the onset or prevent it. ACTC-DS will contribute to a better understanding of Alzheimer’s disease in DS and bring the latest therapies to this population.