Down Syndrome Dementia
What is Down Syndrome Dementia?
Down syndrome (Trisomy 21) is a condition characterized by the presence of extra material on chromosome 21. People living with Down syndrome have an increased risk of developing dementia as they get older. Dementia associated with Down syndrome is thought to be very similar to traditional forms of Alzheimer’s disease.
More than 75 per cent of people with Down syndrome aged 65 and older are living with Alzheimer’s disease, about six times the number of people in the greater population in the same age group. The risk of developing Alzheimer’s disease in individuals with Down syndrome has been found to increase with advancing age.
Since people with Down syndrome typically live up to 55-65 years of age, they are more likely to have young-onset Alzheimer’s disease rather than the classical type that affects individuals older than 65 years.
People with Down syndrome have been found to have significant levels of plaques and tangles in brain nerve cells – a common feature of Alzheimer’s disease – appearing by the age of 40. Surprisingly enough, not everyone with these brain changes develops symptoms of Alzheimer’s disease. It is not known why some people with Down syndrome who have brain changes develop symptoms - while others do not.
What are the symptoms?
In people living with Down syndrome, changes in overall function, personality and behavior may be more common as early signs of Alzheimer's disease than memory loss. Early symptoms may include:
- Lack of interest in socializing, communicating or expressing thoughts
- Lack of initiative and enthusiasm for common activities
- Decreased ability to focus or concentrate
- Emotional changes such as sadness, fearfulness, anxiety or irritability
- Behavioural changes including aggression, restlessness or sleep disturbances
- Seizures that begin in adulthood
- Changes in coordination and walking
- Increased noisiness or excitability
Researchers are unclear as to why these symptoms differ for people with Down syndrome compared to the general population.
Is it genetic? Can it be passed on to family members?
It is believed that the extra chromosome 21 is responsible for the symptoms of dementia in individuals with Down syndrome. One of the chromosome 21 genes in Down syndrome codes for amyloid precursor protein (APP). The exact function of APP is not known, but it is believed that day-to-day brain activity involves continuous "processing" of APP into shorter pieces. One of the brain's APP processing pathways produces beta-amyloid, the chief component of plaques and a prime suspect in Alzheimer’s disease. Having an extra copy of the APP gene may increase the production of beta-amyloid and trigger the chain of biological events leading to Alzheimer's disease.
How is it diagnosed?
Diagnosing dementia in a person with Down syndrome can be difficult because of the challenges involved in assessing changes in cognitive skills in people with intellectual disabilities. The following guidelines have been recommended:
- Document baseline adult function by age 35. Ideally, each individual's medical record should include detailed information about adult abilities and intellectual, social and behavioral functions.
- Watch for changes in day-to-day function. Reduced enthusiasm for daily activities, lack of interest in social interactions and changes in personality and behavior are often early signs.
- Consider professional assessment by a dementia expert. A variety of cognitive tests have been used to evaluate thinking changes in adults with Down syndrome. Keep in mind that cognitive tests should never be used as the only benchmark to diagnose dementia in a person with Down syndrome.
- Rule out other causes of symptoms. Thyroid conditions, depression, chronic ear and sinus infections and sleep apnea can cause changes in a person's thinking and functioning.
What kind of treatment is available?
Currently there are no approved pharmaceutical drugs used specifically to treat dementia associated with Down syndrome. In the United Kingdom, cholinesterase inhibitors (a class of medications approved to treat Alzheimer's disease), are approved to treat dementia in people with Down syndrome. However, there isn't enough evidence to reach a definitive conclusion about their effectiveness.
An international clinical study has shown no benefit for the Alzheimer's drug Memantine (Ebixa) in adults with Down syndrome. More research and clinical studies are required to identify effective treatments for dementia in those with Down syndrome.
This content is provided for informational purposes only and is not to be used for diagnosis or treatment of any type of dementia or its symptoms. Any mention of pharmaceutical interventions or treatments is not an endorsement by the Alzheimer Society of Calgary. This information is apt to change at any time without notice. For medical advice, please contact your physician.
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