Researchers have taken a major step towards a blood test that can predict the risk of developing dementia more than a decade before patients are officially diagnosed with the disease, The Guardian writes.
Hopes for the test grew after scientists discovered biological markers of the disease in blood samples collected from more than 50,000 healthy volunteers participating in the UK's Biobank project.
The blood test revealed patterns of four proteins that predicted the onset of dementia in general, and Alzheimer's disease and vascular dementia in particular, in old age.
Combined with more traditional risk factors such as age, gender, education and genetic predisposition, the protein profiles allowed researchers to predict dementia with approximately 90% accuracy nearly 15 years before people had clinical confirmation of the disease.
More than 55 million people worldwide suffer from dementia, and this figure is expected to reach 78 million by 2030, notes The Guardian. About 70% of all dementia cases are caused by Alzheimer's disease, with vascular dementia, caused by damage to blood vessels, accounting for 20% of cases.
“We hope to develop this as a screening kit that can be used in the National Health Service,” says Professor Jianfeng Feng, who holds appointments at the University of Warwick and Fudan University in China.
A number of recent studies have demonstrated the potential of blood tests to identify patients most likely to develop dementia. Armed with such information, physicians could determine which patients should be expedited for further evaluation, including full diagnostic testing for Alzheimer's disease.
Early confirmation of the disease is critical if patients are to benefit from two new Alzheimer's drugs, lecanemab and donanemab, which are under review by the UK's medicines regulator. If licensed, the National Institute for Health Care Excellence will consider the costs and benefits before deciding whether it should be provided to the NHS.
Since a synthetic antibody drug made by Biogen in the US and Eisai in Japan hit the headlines in 2022 to slow the progression of Alzheimer's disease, doctors and medical charities have warned that the health service is not prepared to supply such drugs.
For patients to receive these drugs, they must have early stage Alzheimer's disease and a lumbar puncture or PET scan to confirm the presence of amyloid protein in the brain. Toxic amyloid accumulations are one of the hallmarks of Alzheimer's disease. But Alzheimer's Research UK estimates that only 2% of eligible patients undergo such testing.
Work is underway to develop and implement simple blood tests to diagnose Alzheimer's disease, but even with rapid diagnosis, challenges remain. New drugs must be administered to patients every two weeks, and because of potentially fatal side effects, patients require regular MRI scans to check for brain swelling or bleeding.
For the latest study, blood samples from 52,645 UK adults without dementia were collected and frozen between 2006 and 2010 and analyzed 10 to 15 years later. More than 1,400 participants developed dementia.
Using artificial intelligence, the researchers looked for links between nearly 1,500 blood proteins and the development of dementia years later. Writing in the journal Nature Aging, they describe how four proteins, Gfap, Nefl, Gdf15 and Ltbp2, were present in unusual amounts in those who developed all-cause dementia, Alzheimer's disease or vascular dementia.
Higher levels of proteins were warning signs of the disease. Inflammation in the brain can cause cells called astrocytes to overproduce Gfap, a known biomarker for Alzheimer's disease. People with elevated Gfap levels were more than twice as likely to develop dementia as people with lower levels.
Another blood protein, Nefl, is associated with damage to nerve fibers, while higher than normal levels of Gdf15 can be observed after damage to blood vessels in the brain. The scientists found that increases in Gfap and Ltbp2 levels were highly specific to dementia and not to other brain diseases, with changes occurring at least 10 years before people were diagnosed with dementia.
The researchers are in talks with companies to develop the test but said the cost, currently several hundred pounds, would need to come down to make it viable.
Dr Shona Scales, director of research at Alzheimer's Research UK, said: “This new study adds to a growing body of evidence that studying the levels of certain proteins in the blood of healthy people can accurately predict dementia before symptoms develop.”
Further research is needed to understand how well such tests work in more diverse populations. Dr. Scales adds: “Even when tests show promising results in studies like this, they still must pass regulatory approval before they can be used in medical settings.”