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expert reaction to study of β-Amyloid burden and cognitive changes as published in Neurology

A paper in the journal Neurology showed that high levels of the protein amyloid beta in the brain, which is correlated with Alzheimer’s disease, is also associated with decreased brain function in healthy adults.

Dr Anne Corbett, Research Manager, Alzheimer’s Society, said:

“We have known for some time that changes in the brain happen many years before symptoms of dementia appear. We don’t yet know whether the lower brain performance recorded here is happening to healthy people or to people who are in the very early stages of Alzheimer’s.

“Improving our understanding of what causes Alzheimer’s and other sorts of dementia is essential if we are to move forward with drug development and ultimately find a cure. One in three people over 65 will die with dementia yet there is currently eight times less spent on dementia research than cancer research. We must invest now.”

Additional information from the Alzheimer’s Society: Alzheimer’s hallmark could affect brain function of healthy adults, study claims. High levels of the protein amyloid beta in the brain – a hallmark of Alzheimer’s disease – could also be associated with the memory and mental function of healthy adults according to a study published in Neurology today (Wednesday 1 February 2012). Scientists from the University of Texas took brain scans of 137 people aged 30 to 89 who did not have dementia. Participants were also tested for the gene APOE4 which is known to increase risk of Alzheimer’s. “They found around 20 per cent of adults aged 60 and older had significantly elevated levels of amyloid beta. Higher levels of this protein were linked with lower test scores related to working memory, reasoning and speed of processing information.

Derek Hill, Professor of Medical Imaging Science at University College London and CEO of IXICO, said:

“Alzheimer’s Disease (AD) is characterised by small lumps of protein – amyloid plaques – in the brain. For more than a century, these have been seen under the microscope in the brains of people who have died of AD. More recently, it has become clear that these amyloid plaques build up in the brain years or even decades before dementia sets in. It is now possible to image these amyloid plaques when people are still alive and well using a PET scanner. In this study, more than 100 entirely normal people from age 30 – 89 had these amyloid PET scans. These people also had their cognition (brain performance), including memory, tested. When the researchers compared the brains of these individuals, they found both that the amount of amyloid plaques increase in older people, and also that higher amount of amyloid plaque is associated with poorer cognition, even in those people who seem entirely normal. This helps understand the very earliest stages of Alzheimer’s Disease.

“These finding are of practical interest because most attempts to develop treatments for Alzheimer’s Disease involve targeting the amyloid plaques that build up in the brain. This study confirms that these plaques can build up decades before people get dementia, and also suggests that the build-up of these plaques in the brain – even when people are entirely normal – can have a detectable detrimental effect on their cognition. This is likely to increase the interest in treating Alzheimer’s long before dementia sets in. The next stage of their research will be even more compelling – when the same people have a repeat PET scan to find out how each individual’s change in cognition is linked to the change in the amount of amyloid plaques in their brains.”

John Hardy, Professor of Neuroscience, University College London, said:

“This work shows that a sizeable proportion of elderly individuals die in the early stages of Alzheimer’s disease, and that these individuals do show some subtle clinical signs. As life span increases, this work shows clearly that as life expectancy increases, the number of Alzheimer cases will increase. This work illustrates the desperate need we as a society have for therapies which attack the disease process.”

David Allsop, Professor of Neuroscience, Lancaster University, said:

“The build-up of amyloid in the brain is a prominent feature of Alzheimer’s disease, and may actually begin many years before this disease is diagnosed.

“This study involves the use of a sophisticated brain imaging technique to detect these amyloid deposits in apparently normal people. It was found that about 1/5 people over the age of 60 have elevated levels of amyloid in their brains, and these people perform less well in memory tests than those without any amyloid deposits.

“This is an important finding because it suggests that the formation of amyloid in the brain is a direct cause of memory loss, and this link has been very difficult to prove in humans.

“However, we do not know yet if the people with the amyloid deposits in their brains will actually go on to develop Alzheimer’s disease. This will be an important next step in this type of research.

Preventing the accumulation of amyloid in the brain, at a very early stage, is one of the key approaches under development for the more effective treatment of Alzheimer’s disease.”

‘β-Amyloid burden in healthy aging: regional distribution and cognitive consequences’ by Rodrigue, K.M. et al., published in Neurology on Wednesday 1st February.

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