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Does Down’s syndrome hold the key to cracking Alzheimer’s?

Dr Laura PhippsKirsty MaraisClaire LucasRobin BrisbourneKaty StubbsFaye MonkEd Pinches

It can come as a surprise to know that having Down’s syndrome puts people at much higher risk of Alzheimer’s. In fact, the genetic rearrangement that causes Down’s syndrome is one of the greatest genetic risk factors for Alzheimer’s.

Sadly, everyone with Down’s syndrome will have developed the characteristic plaques and tangles of Alzheimer’s in their brain by the age of 30, and around half will be diagnosed with dementia by the time they reach 50.

So what progress is being made to understand dementia risk in this important group of people?

The reasons for risk

People with Down’s syndrome are born with an extra copy of chromosome 21, a stretch of DNA that houses 240 different genes. We’ve blogged about this before, but at the Alzheimer’s Association International Conference this week we heard how research is unpicking the genes that are driving this risk.

Chromosome 21 harbours a gene called APP, responsible for making the Alzheimer’s protein, amyloid. This is one key reason why people with Down’s syndrome develop the disease at a far faster rate. But your donations are helping Dr Francis Wiseman at University College London show that other genes on chromosome 21 aren’t entirely innocent either.

Her team has identified another gene that appears to speed up the development of key Alzheimer’s changes in mice. She also highlighted how these 240 extra genes can cause subtle differences in the biology of how cells work. Her team is now working hard to understand the influence of these changes on Alzheimer’s risk.

A high priority population

Dr Andre Strydom from University College London highlighted that the welcome increases in life expectancy in Down’s syndrome over recent decades also means that more are experiencing Alzheimer’s too, making them a vital group to work with to advance research efforts.

He explained that people with Down’s syndrome tend to perform better on cognitive assessments that focus on objects and environments rather than words. So current diagnostic tests used to assess memory and thinking in the general population can be a barrier to setting up high quality research studies in Down’s syndrome.

As part of the LonDownS consortium – a mixing pot of clinicians, geneticists, developmental psychologists, psychiatrists and cellular scientists – researchers are creating more sensitive and relevant memory and thinking assessments for people with Down’s syndrome. This will make it easier to detect early changes in dementia and allow doctors and researchers to better help people.

A window of opportunity

Because people with Down’s syndrome are at such high risk of dementia, they are a key group of people to help researchers understand the natural history of Alzheimer’s, beginning decades before symptoms start. And as Prof Bill Mobley from the University of California San Diego said at AAIC17, “we all benefit so much from our interaction with folks with Down’s syndrome”.

From his experience, people living with Down’s syndrome are ready and able to get involved in studies, and that’s our experience too.

Meet Russell Ramsey. He’s taking part in a research study that you’re helping to fund at the University of Cambridge. That study, led by Prof Tony Holland, is following a group of people with Down’s syndrome with brain scans and memory tests to understand how Alzheimer’s develops and identify a key window of opportunity to intervene with clinical trials of new treatments in future. This study is being funded by money raised by runners taking part in the famous Chariots of Fire relay race in Cambridge on Saturday 17 September.

““I have two family members who have Alzheimer’s and it is so sad. I wanted to help with this study to help people with Alzheimer’s in the future. People who have Down’s syndrome like me and other people.” Russell Ramsey

Prof Micheal Rafii from California also spoke of his team’s work to map the early development of Alzheimer’s and we heard of a 5-year US study of 500 people with Down’s syndrome, the largest of its kind to follow how Alzheimer’s develops over time.

Studies so far in Down’s syndrome suggest that key changes in the brain start around 15 years before symptoms show, mirroring similar patterns seen in the wider population. This is important, as it suggests that understanding what happens in the brain in Down’s syndrome will not only bring benefits for this important group of people, but potentially for everyone affected by the disease.

Treatments on the horizon

While most clinical trials of new Alzheimer’s treatments aren’t being done in people with Down’s syndrome, researchers acknowledged the great importance of involving people with Down’s syndrome in clinical trials for new medicines. We heard of several treatments already being trialled in people with Down’s syndrome, but with this area of research gaining momentum, we are positive that more studies will follow. And with Alzheimer’s having such a huge impact on people with Down’s syndrome, these studies can’t come soon enough.

  • Help us support pioneering research into Alzheimer’s in Down’s syndrome by entering a team in Chariots of Fire this September. Have you signed up a team yet?
  • If you have Down’s syndrome and would like to get involved in research studies, you can sign up to Join Dementia Research online or by calling us on 0300 111 5 111.
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