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.
During the study, published in Neurology, 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.
Alzheimer's Society comment:
'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.'
Dr Anne Corbett