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

An illustration from the US National Institute on Ageing depicts cells in an Alzheimer’s-affected brain. The brown areas are clumps of protein that disrupt cell functions.  AP
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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.

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“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.

Updated: January 27, 2023, 12:01 AM