Are people who have Down syndrome at greater risk for developing Alzheimer's disease?
Yes, it appears that people with Down syndrome are at greater risk for developing Alzheimer’s disease. According to the Down Syndrome Society, Alzheimer’s disease is diagnosed in about 30 percent of people with Down syndrome in their 50s and in about 50 percent of those in their 60s.
Why are people with Down syndrome at greater risk for developing Alzheimer’s disease?
Scientists believe the increased risk is due to the extra chromosome, chromosome 21, that causes Down syndrome. Persons born with Down syndrome have three copies (instead of the normal two copies) of this chromosome. Scientists have identified several genes on chromosome 21 that are responsible for certain aspects of the aging process. They believe the extra full or partial chromosome contributes to the increased risk of Alzheimer’s disease seen in people with Down syndrome. In addition, genes on chromosome 21 produce a key protein, amyloid precursor protein, which plays an important role in the brain changes that are specifically seen in Alzheimer’s patients.
Symptoms and Causes
What are the symptoms of Alzheimer's disease in people with Down syndrome?
The symptoms of Alzheimer’s disease in people with Down syndrome may be different than those typically seen in others with Alzheimer’s disease. For example, in the early stages of the disease, memory loss may not be the first change noted. In fact, it may be difficult to notice symptoms of Alzheimer’s disease because of the already present limitations in memory and functioning in the person with Down syndrome. More often, the early changes seen in people with Down syndrome may be those affecting personality, behavior, and overall function.
More specifically, these symptoms may include:
- Decreased interest in social interaction
- Less interest in hobbies and previously “loved” activities and events
- Increase in irritability, agitation, aggressiveness, sadness, anxiety
- Loss of previously mastered skills
- Changes in sleep pattern, more restlessness
- Lowered attention span; loss of concentration
- Increase in compulsions
- Onset of negative and self-critical comments
- Onset of confusion/disorientation
- Loss of energy, tiredness, loss of “spark for life”
- Loss of ability to complete tasks with multiple steps
- Loss of balance/coordination when walking
- Development of seizures
Diagnosis and Tests
How is the diagnosis of Alzheimer’s disease made in a person with Down syndrome?
The diagnosis of Alzheimer’s disease can be difficult in a person with Down syndrome because of the intellectual disability already present. The knowledge of close family members is especially important and useful information for the doctor. A close family member knows the baseline capabilities – the intellectual and functional abilities – of their loved one with Down syndrome and are usually the first person to notice changes. It is also helpful to find a memory specialist (a neurologist, psychiatrist, geriatrician) who is trained in diagnosing people who have intellectual disabilities.
The doctor will assess the patient using a variety of “thinking” tests adapted for a person with Down syndrome as well as perform tests and lab work to rule out other causes of the symptoms.
Experts recommend that the close family member of the person with Down syndrome do the following to assist in a possible diagnosis:
- Get a full intellectual, social, and behavior assessment of your loved one by the age of 35. Make sure the results of the assessment are documented in his or her medical record. This assessment will be useful as the baseline to which future changes will be compared.
- Keep a journal of any changes in the day-to-day behavior of your loved one with Down syndrome (look for the symptoms mentioned above).
Management and Treatment
What treatments are available for treating Alzheimer’s disease in a person with Down syndrome?
There are no specific drugs approved to treat the co-existing conditions of Alzheimer’s disease and Down syndrome. Two drug types are available to treat Alzheimer’s disease -- the cholinesterase inhibitors (donepezil [Aricept®], rivastigmine [Exelon®], and galantamine [Razadyne®]) and the NMDA receptor antagonist memantine [Namenda®]. Unfortunately, there is not much evidence to support the use of either class in patients with both conditions. There’s not enough scientific evidence to conclude that the cholinesterase inhibitors are helpful in patients with Down syndrome and memantine has shown no benefit in these patients in a large clinical trial.
Several drugs that target some of the genetic and chemical changes in the brain that occur in people with Down syndrome and Alzheimer’s disease are currently being examined in very early (animal studies) clinical trials. Although scientists are generally encouraged by these early results, many more years of testing will be needed before these drugs may come to market and/or will be recommended for use in these patients.