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Down syndrome and Alzheimer's disease

Key points

  • Down syndrome is a genetic condition where people are born with an extra (third) chromosome 21. If you have Down syndrome, you have a higher chance of developing Alzheimer’s’ disease, a brain condition that affects your memory, thinking and behaviour.

  • Diagnosing Alzheimer’s’ disease in people with Down syndrome can be difficult as Alzheimer’s symptoms may be considered part of the Down syndrome.

  • There is no cure for Alzheimer’s disease, but it can be managed and some symptoms can be treated. Support is available.

About Alzheimer’s disease and Down syndrome

Down syndrome is a condition where you are born with three versions of chromosome 21 in every cell instead of two. This extra chromosome causes developmental problems and health issues, affecting learning, language and memory.

Alzheimer’s disease is a brain condition that affects your memory, thinking and behaviour. It’s the most common form of dementia. For more information, see our Alzheimer’s disease page.

If you have Down syndrome, you are more likely to develop Alzheimer’s disease, and at a younger age. People with Down syndrome make 1.5 times as much of a substance called amyloid precursor protein as other people. This seems to cause earlier Alzheimer’s disease symptoms in people with Down’s syndrome.

Not everyone with Down syndrome develops dementia. Around half of all people with Down syndrome will develop Alzheimer’s disease by age 60. The average age when symptoms start is the early to mid-50s.

By age 40, almost all people with Down syndrome have changes in their brains associated with Alzheimer’s disease. You may not have symptoms of Alzheimer’s at this age, but they can develop in the future.

However, some people with Down syndrome who are over 40 show no signs of Alzheimer’s disease. We don’t yet know exactly why this happens.

There is no known cure for Alzheimer’s disease. But there is support to help you live your best possible life.

Early warning signs of Alzheimer’s disease in people with Down syndrome

Someone with Down syndrome who is developing Alzheimer’s disease may experience:

  • changes in sleep patterns
  • finding routine daily tasks harder than usual
  • reduced short-term memory
  • disorientation and confusion
  • trouble becoming motivated and starting tasks
  • increased difficulties understanding language
  • reduced interest in being socially active
  • reduced communication skills
  • restlessness
  • sadness, fearfulness or increased anxiety.

If you notice these symptoms in yourself or someone you know who lives with Down syndrome, talk to your doctor.

Diagnosing Alzheimer’s disease in people with Down syndrome

A medical specialist will only make a diagnosis of Alzheimer’s disease after careful assessment. If you’re living with Down syndrome, you may have pre-existing challenges with thinking, memory and daily living skills. This can make a diagnosis difficult, because:

  • you are more likely to have other conditions that can be mistaken for Alzheimer’s disease, like hypothyroidism and depression
  • the side effects of some medications can mimic Alzheimer’s disease
  • the usual skill tests used for diagnosis don’t take into account your existing problems or challenges
  • if you have limited communication skills, it may affect the assessment.

Document your baseline functioning

One way to make this process easier is to document your baseline functioning. This means making a record of your thinking, memory, communication skills, mood and more before any changes, so the doctor can make a better comparison later.

If you’re under 35 and have Down syndrome, documenting your baseline functioning can be very helpful. Talk to your doctor.

Seeking support

For more information and support on Down Syndrome, see:

Dementia expert webinar: Down syndrome and dementia, with Dr Sushmita Hunter

How Dementia Australia can help

Whatever your experience of dementia, we're here for you.

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Last updated
13 November 2023