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Dementia ‘highly prevalent’ among women with Down syndrome

Author of new study calls on Government to ensure services for often vulnerable group

A study of dementia in women with Down syndrome in Ireland has found very high prevalence rates. Image: iStock.

A study of dementia in women with Down syndrome in Ireland has found very high prevalence rates and significantly earlier onset of the disease than in the general population.

More than 97 per cent of those in the study developed dementia over a 20-year period, researchers from Trinity College Dublin found. The average age of onset of dementia was 55 years.

The risk of developing dementia in people with Down syndrome was estimated at 23.4 per cent at age 50, 45 per cent by age 55 and 88 per cent at the age of 65.

In contract, the prevalence of dementia in the general population is estimated at between 4.3 per cent and 8.6 per cent in people aged 65 years and over.

It was previously thought people with Down syndrome lived only three to five years on average after developing dementia. However, the study published in the Journal of Intellectual Disability Research found the average length of survival was seven years, with some women living with dementia for 20 years.

This data has major implications from a care and resources perspective, according to the study.


Further, about 80 per cent of people with Down syndrome and dementia will go on to develop new onset epilepsy. The corresponding figure for the general population is 11 per cent.

Lead author Prof Mary McCarron called on the Government to introduce measures to ensure services and care for people with Down syndrome adequately reflecting these realities.

The international recommendation was for people with Down syndrome to have a baseline assessment at the age of 35 years, she said, but this was more often “the exception rather than the norm” in Ireland. As a result, many people with Down syndrome were not diagnosed until dementia was at an advanced stage.

The study followed 77 women with Down syndrome over the age of 35 who were enrolled in 1996 and assessed at a specialist memory clinic at the Daughters of Charity Disability Support Service.

“Clearly, radical changes need to be made in order to respond and address the needs of this often vulnerable group of people to help diagnose, support, treat and help prevent dementia.

“We need to support people with Down syndrome and dementia to live in the home of their choice with their family or friends for as long as possible. Supports should include appropriate dementia specific respite services for family and/or peers in group homes.”

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