What Is Alzheimer’s disease?
Alzheimer's disease is a slowly progressive degenerative brain disease that causes memory problems, disorientation, and confusion. Alzheimer's progresses to dementia and eventually causes physical problems such as trouble with swallowing and motor coordination, and ultimately leads to death. Alzheimer's is the most common form of dementia in the U.S. and is typically a disease of old age. Up to 95% of people diagnosed with Alzheimer's disease are older than age 60. Up to 6% of the population of people over the age of 60 has Alzheimer's disease. The rate of Alzheimer's disease in people with Down syndrome is much higher -- about 25% of adults age 40 and above and about 65% for adults age 65.
What Causes Alzheimer’s Disease?
The mechanisms that cause Alzheimer's disease are not completely understood. We do know that there is accumulation of certain proteins, beta-amyloid and tau, in the brains of patients with Alzheimer's. Beta-amyloid may deposit as "plaques" in between neurons, while tau can accumulate as "tangles."
These plaques and tangles cannot be seen by imaging techniques such as MRI or CAT scans. They can only be seen after death during an autopsy.
What Is the Connection Between Alzheimer's Disease and Down Syndrome?
Alzheimer's disease is a disease of aging. Because people with Down syndrome show premature aging, they are at higher risk to develop Alzheimer's disease and to develop it at an earlier age than normal.
In fact, it is estimated that by:
- Age 40 to 49, 10% to 25% of people with Down syndrome have Alzheimer's disease.
- Age 50 to 59, 20% to 50% of people with Down syndrome have Alzheimer's disease.
- Age 60 or greater, 60% to 75% of people with Down syndrome have Alzheimer's disease.
It is thought that the increased risk to develop Alzheimer's disease in people with Down syndrome is related to the extra copy of chromosome 21 (the cause of Down syndrome). It is thought that having an extra number 21 chromosome causes increased production of beta-amyloid, leading to the early formation of plaques in the brains of people with Down syndrome.
It is also known that by age 40, all individuals with Down syndrome have accumulated beta-amyloid plaques in their brains. However, not all individuals with Down syndrome will have symptoms of Alzheimer’s at this point in their lives. It is unclear why some people with Down syndrome develop early Alzheimer's disease and others do not.
How Is Alzheimer's Disease Diagnosed?
Alzheimer's disease is difficult to diagnose definitely. No single blood test or imaging technique will let a doctor make the diagnosis. Ultimately, the diagnosis of Alzheimer's disease is made after a person has died at autopsy, when the plaques and tangles are seen in the person’s brain.
While alive, a person will be given a presumptive diagnosis of Alzheimer's disease based on signs such as memory loss and confusion, and imaging studies (CAT scan or MRI) that show atrophy or shrinkage of certain parts of the brain.
While there are standardized tests that can be used in the non-Down syndrome population to measure memory loss and other cognitive functioning, these tests are often not that useful in diagnosing Alzheimer’s disease in people with Down syndrome due to their underlying cognitive disability. In people with Down syndrome, it is often more helpful to document loss of functional abilities such as the ability to take care of one’s self.
Because other diseases such as depression and hypothyroidism can have symptoms in common with early Alzheimer's disease, it is important to make sure that a person with Down syndrome does not have one of these treatable conditions rather than Alzheimer's disease.
What Is the Treatment for Alzheimer's Disease?
Currently, there is no cure for Alzheimer's disease. However, some treatments focus on helping some of the specific symptoms of Alzheimer's disease and helping delay or slow the progression of the disease.
Most of these treatments are relatively new and have not been tested specifically in people with Down syndrome. It is important to work with a doctor who is familiar with Alzheimer's disease and Down syndrome to devise an appropriate treatment plan for an individual with Down syndrome.
Resources and Support Groups
Alzheimer’s Disease Education and Referral (ADEAR) Center
P.O. Box 8250
Silver Spring, MD 20907-8250
225 N. Michigan Avenue, Floor 17
Chicago, IL 60601-7633
Alzheimer’s Foundation of America
322 Eighth Avenue, 7th Floor
New York, NY 10001
866-AFA-8484 (866-232-8484; toll-free)
Cassidy, Suzanne B. , Allanson, Judith E., (2001) Management of Genetic Syndromes. 1st ed. New York, NY; 2001.Norberto Alvarez, MD, Emedicine, Behavioral Neurology and Dementia Alzheimer Disease in Individuals With Down Syndrome, 2008.