A simple blood test that diagnoses Alzheimer's a decade before symptoms start has been developed. Scientists have identified key chemicals linked to the devastating memory-robbing disease.
The sugar molecules, called glycans, flag rogue brain proteins that destroy neurons. It paves the way for a simple and cost-effective screening programme for older people.
Medications or lifestyle changes would be prescribed when they are most likely to be effective. The technique is 80 per cent accurate. Dementia cases worldwide will triple to more than 150 million by 2050.
Early diagnosis and treatment is crucial to combat the growing health crisis. First author Robin Zhou, a medical student at the Karolinska Institute in Stockholm, said: "The role of glycans, structures made up of sugar molecules, is a relatively unexplored field in dementia research.
"We demonstrate in our study that blood levels of glycans are altered early during the development of the disease. This could mean we'll be able to predict the risk of Alzheimer’s disease with only a blood test and a memory test."
Currently, PET (positron emission tomography) scans or painful spinal lumbar punctures are required for clinical diagnosis. Both are costly. Identifying tau biomarkers in blood samples is an urgent and unmet need. The breakthrough is a potential game-changer.
Alzheimer's is believed to be caused by the abnormal accumulation of tau and another protein known as amyloid beta. They gather in tangles and clumps, respectively. Drug trials have failed to date is they are given to recipients too late - once the condition has taken hold.
The Swedish team found those with high levels of a glycan named GlcNAc (bisecting N-acetylglucosamine) are most prone to the disease. It adds to their previous evidence of a link. But these analyses were done on cerebrospinal fluid.
Glycans lie on the surface of proteins, the building blocks of life, determining their location and function in the body. Individuals with matching amounts of glycans and tau were over twice as likely to develop Alzheimer's.
Corresponding author Dr Sophia Schedin Weiss, said: "We also show a simple statistical model that takes into account blood glycan and tau levels, the risk gene APOE4 and a memory test, can be used to predict Alzheimer's disease to a reliability of 80 per cent almost a decade before symptoms such as memory loss appear."
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Results were based on blood samples from 233 members of the Swedish National Study on Ageing and Care. They were monitored regularly with respect to factors such as memory loss and the presence of dementia.
Follow-ups were carried out every three to six years and continued for 17 years. The researchers will now be analysing blood samples from thousands of remaining participants as well as those from similar studies in Sweden and other countries.
Dr Schedin Weiss said: "We're collaborating with researchers in primary care in Sweden to evaluate different biomarkers for dementia at primary health care centres. We hope glycans in the blood will prove to be a valuable complement to current methods of screening people for Alzheimer's disease that will enable the disease to be detected early."
The findings are published in the journal Alzheimer's & Dementia.
