Blood Test Predicts Alzheimer's Risk 3.5 Years Before Clinical Diagnosis

A new study has found that a blood-based test can predict the risk of Alzheimer’s disease up to 3.5 years before clinical diagnosis. The study is based on the idea that components in the human blood are capable of modulating the formation of new brain cells, a process called neurogenesis which occurs in the hippocampus that plays a role in learning and memory. Alzheimer’s disease affects the formation of new brain cells in the hippocampus during its early stages, although previous research has managed to study neurogenesis only in its later stages by using autopsies.

Researchers at King’s College London (London, UK) set out to understand the early changes by collecting blood samples over a period of several years from 56 individuals with Mild Cognitive Impairment (MCI), a condition in which there is worsening of memory or cognitive ability. Not all individuals experiencing MCI can go on to develop Alzheimer’s disease, although those with the condition are diagnosed at a much higher rate compared to the wider population. Out of the 56 participants in the study, 36 went on to be diagnosed with Alzheimer’s disease.

In their study of how blood affected the brain cells, the researchers made a number of key discoveries. The participants from whom blood samples were collected over the years and who subsequently deteriorated and developed Alzheimer’s disease exhibited a decline in cell growth and division and a rise in apoptotic cell death (a process by which cells are programmed to die). However, the researchers found that these samples also upped the conversion of immature brain cells to hippocampal neurons.

The key reasons behind the increased neurogenesis are not yet known, although the researchers believe that it could be attributed to an early compensating mechanism for the neurodegeneration (loss of brain cells) experienced by individuals developing Alzheimer’s disease. Upon using only the blood samples collected furthest away from when the participants were diagnosed with Alzheimer’s disease, the researchers discovered that the changes in neurogenesis took place 3.5 years before a clinical diagnosis. These findings provide an opportunity to further understand the changes occurring in the brain at the earliest stages of Alzheimer’s disease, according to the researchers.

“Our findings are extremely important, potentially allowing us to predict onset of Alzheimer’s early in a non-invasive fashion,” said Dr. Edina Silajdžić, 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).”

“It is now essential to validate these findings in a bigger and more diverse group of people,” added Dr. Hyunah Lee, the study’s joint first author. “We are excited about the potential applications of the blood-based test we used. For example, it can help stratify individuals with memory problems for a clinical trial of disease-modifying drugs for Alzheimer’s.”

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