Blood Test May Detect Alzheimer's Disease 3.5 Years Before Diagnosis

Researchers at King's College London developed a blood-based test that could predict Alzheimer's disease up to 3.5 years before clinical diagnosis.

The study included 56 individuals with Mild Cognitive Impairment (MCI), a decline in memory or cognitive ability. The condition affects between 5% and 20% of people 65 and older and is not severe enough to interfere with daily life. A person who has MCI is usually aware of it.

While having MCI does not necessarily lead to Alzheimer's disease, an estimated 10% to 15% of people living with the condition develop dementia each year. Of the 56 participants in the study, findings of which were published in the journal Brain, 36 were eventually diagnosed with Alzheimer's.

Changes appear years before a diagnosis

The researchers modeled the process of neurogenesis — production of neurons — in a dish using human brain cells and human blood. They treated brain cells with blood taken from people with MCI to see how those cells changed in response to blood as Alzheimer's disease progressed.

Using the blood samples collected furthest away from when the participants received Alzheimer's diagnosis, researchers found that the changes in neurogenesis occurred 3.5 years before a clinical diagnosis.

Moreover, the blood samples collected from participants who developed Alzheimer's disease promoted a decline in cell growth and an increase in apoptotic cell death, the process of programmed cell death.

Researchers say this is the first evidence the human body's circulatory system can affect the brain's ability to form new cells.

"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," says Dr. Hyunah Lee, the study's joint first author, King's Institute of Psychiatry, Psychology & Neuroscience.

Alzheimer's disease affects millions

Alzheimer's disease is the most common cause of dementia, a broad term for memory loss and other cognitive abilities that are severe enough to interfere with daily life.

An estimated 6.5 million Americans 65 and older are living with Alzheimer's, according to 2022 data. Nearly three in four (73%) are aged 75 or older.

Alzheimer's disease typically begins with difficulty remembering new information. The symptoms progress over time and can include mood and behavior changes, disorientation, confusion, difficulty speaking, swallowing, and walking.

The disease has no cure, but two treatments — aducanumab and lecanemab — may help to reduce cognitive and functional decline.