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The research, published in the journal Alzheimer's & Dementia, shows the level of small molecules called microRNA, that are found in blood plasma, dynamically change as the symptoms of the disease get worse.
The team leader of the research, Associate Professor Joanna Williams, said changes can be seen in people's blood when a person has been diagnosed with Alzheimer's.
University of Otago Associate Professor and Alzheimer's researcher Joanna Williams said changes can be seen in people's blood when a person has been diagnosed with Alzheimer's.
Research indicates changes to the molecules in blood occurs long before symptoms appears.
The work will be expanded to allow researchers to establish a biomarker of Alzheimer's and will help move towards the development of a simple blood screening tool to pick up those at risk of developing the disease.
Williams said it is hoped that earlier intervention may mean some of the current therapies for Alzheimer's are more successful.
The research's lead author Diane Guévremont said there is currently no easy early detection method.
"It is possible to quantify levels of toxic molecules in the brain or changes in brain structures, but it is not possible to measure these early changes without repeated use expensive and invasive procedures that are only available in highly specialised centres and not currently suitable for routine screening," she said in a statement.
She said a blood test could prove to be a valuable tool to discover those at risk of development Alzheimer's disease, although it may not be as a precise as a positron emission tomography (PET) scan.
Williams said the research team hopes the findings will allow intervention at a time in the disease where therapies are most likely to be effective.
"Our goal is to use blood as a window into the brain, to find biomarkers that can help us diagnose Alzheimer's disease early, long before symptoms appear, and the brain is too damaged for interventions to be effective," she said in a statement.
More than 70,000 New Zealanders are affected by Alzheimer's disease, and this is predicted to increase to 150,000 by 2050, at a cost of more than $1.7 billion a year.