Clinically significant Alzheimer’s-like pathological features develop in all people with Down’s syndrome by 40 years of age. Almost 40 per cent of people with Down’s syndrome who are 60 years or older have a diagnosis of dementia, although such a finding is not straightforward because of an absence of validated approaches for people with intellectual disabilities.
Dementia in Down’s syndrome is a key clinical challenge, especially as people with Down’s syndrome live longer than they used to, with a high proportion of individuals living to 60 years or beyond. Despite the introduction of antenatal screening in the UK in 1990, the incidence of Down’s syndrome had decreased by only one per cent by 2008.
The study enrolled adults over the age of 40 with Down’s syndrome, and with or without Alzheimer’s, at four learning disability centres in the UK and Norway.
Participants received memantine (88 patients) or a placebo (85) for 52 weeks, with the randomisation balanced according to sex, dementia, age group, total Down’s syndrome attention, memory, and executive function scales [DAMES] score, and centre. The primary outcome was change in cognition and function, measured with DAMES scores and a standard assessment tool called the adaptive behaviour scale (ABS).
Both groups declined in cognition and function but rates did not differ between groups for any outcomes. Ten (11 per cent) of 88 participants in the memantine group and six (seven per cent) of 85 controls had serious adverse events. Five participants in the memantine group and four controls died from serious adverse events.
Professor Clive Ballard, from the Wolfson Centre for Age-Related Diseases at King’s, says: ‘Memantine is not an effective treatment in this group of patients. We believe that this robust finding will have implications for clinical practice and research strategy in the future. Specifically, therapies that are beneficial for people with Alzheimer’s disease are not necessarily effective for the treatment of cognitive impairment or dementia in the context of Down’s syndrome.’
Dr Anne Corbett, Research Manager at Alzheimer’s Society (UK), and co-author said: ‘So little is known about the best way to treat dementia in people with Down’s syndrome. Further investment is urgently needed to develop treatments that are effective in this important group of people.’