New blood test could detect Alzheimer’s disease years before diagnosis

Study results could help to understand changes brain goes through at earliest stages of Alzheimer’s

This illustration made available by the National Institute on Aging/National Institutes of Health depicts cells in an Alzheimer’s affected brain, with abnormal levels of the beta-amyloid protein clumping together to form plaques, brown, that collect between neurons and disrupt cell function. Abnormal collections of the tau protein accumulate and form tangles, blue, within neurons, harming synaptic communication between nerve cells. An experimental Alzheimer’s drug modestly slowed the brain disease’s inevitable worsening, researchers reported Tuesday, Nov. 29, 2022 - and the next question is how much difference that might make in people’s lives. Japanese drugmaker Eisai and its U. S. partner Biogen had announced earlier this fall that the drug lecanemab appeared to work, a badly needed bright spot after repeated disappointments in the quest for better Alzheimer’s treatments. (National Institute on Aging, NIH via AP)Show less

Scientists have discovered a new blood test that could detect Alzheimer’s disease three and a half years before a clinical diagnosis.

The blood-based test that could predict the risk of the condition is the result of new research from the Institute of Psychiatry, Psychology and Neuroscience at King’s College London.

The research supports the idea that components in human blood can influence the formation of new brain cells, a process called neurogenesis.

The process occurs in a part of the brain called the hippocampus, which is involved in learning and memory.

While Alzheimer’s affects the formation of new brain cells in the hippocampus during the early stages of the disease, previous research has been able to study neurogenesis only in its later stages through post-mortem examinations.

To understand the early changes, over a number of years researchers collected blood samples from 56 people with mild cognitive impairment (MCI), a condition where someone will begin to experience a weakening of their memory or cognitive ability.

While not everyone with MCI will develop Alzheimer’s disease, those with the condition progress to a diagnosis at a much higher rate than the wider population.

Thirty-six of the 56 people in the study were later diagnosed with Alzheimer’s.

When the researchers used only the blood samples collected furthest away from when someone had Alzheimer’s disease diagnosed, they found that the changes in neurogenesis occurred 3.5 years before a clinical diagnosis.

New drug appears to improve Alzheimer’s - in pictures

A clinical trial of the drug lecanemab shows it may slow down Alzheimer’s in the early stages. Experts have described it as a breakthrough in tackling the disease. PA

A close-up of a human brain affected by Alzheimer's. Japanese company Eisai and its US partner Biogen developed the drug. AP

An illustration of how Alzheimer’s affects the brain, with abnormal levels of the beta-amyloid protein clumping together to form plaques – brown in this rendering – that collect between neurons and disrupt cell function. Photo: National Institute on Ageing

Sajid Javid, who served as UK health secretary, said Britain's 10-year plan to tackle dementia has a focus on prevention. Photo: Alzheimer's Society

A US advert aimed at loosening proposed restrictions on new Alzheimer's treatments. Photo: Reuters

“Previous studies have shown that blood from young mice can have a rejuvenating effect on the cognition of older mice by improving hippocampal neurogenesis," said Prof Sandrine Thuret, the study’s lead author from the institute.

“This gave us the idea of modelling the process of neurogenesis in a dish using human brain cells and human blood.

“In our study, we aimed to use this model to understand the process of neurogenesis and to use changes in this process to predict Alzheimer’s disease, and found the first evidence in humans that the body’s circulatory system can have an effect on the brain’s ability to form new cells.”

The research showed blood samples collected from people who went on to develop Alzheimer’s disease promoted a decrease in cell growth and division.

They also promoted an increase in apoptotic cell death, the process by which cells are programmed to die, the study found.

While the reasons for the increased neurogenesis remain unclear, the researchers suggest it may be an early compensating mechanism for the loss of brain cells experienced by those developing Alzheimer’s disease.

“Our findings are extremely important, potentially allowing us to predict onset of Alzheimer’s early in a non-invasive fashion," said Dr Edina Silajdzic, the study’s joint first author.

“This could complement other blood-based biomarkers that reflect the classical signs of the disease, such as the accumulation of amyloid and tau [the ‘flagship’ proteins of Alzheimer’s disease].”

The findings were published in the journal Brain.