Dementia risk associated with Down syndrome

Four in five people with Down syndrome who reach the age of 65 will develop dementia but many cannot access appropriate care due to their young age or difficulties in securing a diagnosis, a leading expert has said.

Research has found that 80 per cent of those with Down syndrome who reach 65 years of age will have dementia by then with an average onset age of 52. That figure compares with 4.5- 8.6 per cent in the general population.

However, because memory clinics used to treat dementia are not always suited to those who develop the condition in their 40s and 50s, many younger people with Down syndrome have difficulties accessing services. There are also shortfalls in the expertise required to diagnose the illness accurately.

“I have a drawer full of people looking for assessment,” Prof Mary McCarron, director of the Trinity Centre for Ageing and Intellectual Disability, said, explaining that much was required to expand diagnostic capabilities.

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Prof McCarron was among a number of international experts who addressed a Trinity College summit on the subject coinciding with World Down Syndrome Day on Thursday.

In one case she recalled, she met a mother in her 80s who had travelled to Dublin from Kerry with her son, aged in his 50s, who had Down syndrome and advanced dementia.

“They were both incredibly distressed,” she said of the toll the journey had taken on them in a bid to seek out professional help. Many others simply never do and Prof McCarron believes there are now hundreds of people with Down syndrome in need of diagnosis and only a few pockets of service provision equipped to do so.

“I have seen a number of people who are literally at an advanced stage of dementia and they have never had a diagnosis,” she said.

Longer life expectancy

With modern improvements in medical care, those with Down syndrome generally live well into their 50s, compared with a life expectancy of about 12 years in the 1930s. While there is no firm data on how many reach the age of 65, Prof McCarron said most now live “at least to the age of risk of developing dementia”.

A new specialised memory clinic for people with intellectual disability is under development and will act as a centre of excellence for diagnostics as well as establishing satellite clinics around the country.

The complexities of diagnosis relate to the broad range of ability sets among those with Down syndrome and the ability of clinicians to differentiate between health conditions that may affect memory – not every case is the result of dementia.

Diagnostic tools employed in standard memory care centres “are simply not helpful in terms of diagnosing those with Down syndrome”, Prof McCarron explained.

“It takes considerably longer; you are not going to bring someone with an intellectual disability into a very busy clinic and [give them the appropriate level of care] in a very short period of time.”

Annual standards

As well as awareness and professional training, Prof McCarron said the gold standard of care would be to deliver annual screening for dementia among those with Down syndrome from as young as 35 years.

Such an approach is critical both for understanding the development of the illness and also for its treatment, she said; many available drugs work only when prescribed at an early stage.

Prof McCarron said a major regret was that people with Down syndrome had been historically omitted from clinical trials and research, possibly because there was nobody to push the agenda or because they made up a relatively small section of society. “It really is quite a tragedy,” she said.

This exclusion is particularly significant given the potential for that population, and its genetic predisposition to the condition, to help inform a broader understanding of it and its treatment, she said.