Gulf News: Dubai: A simple blood test could soon tell you not just whether you're at risk of Alzheimer's disease but roughly when symptoms might begin.

A study published in Nature Medicine on February 19 has brought scientists a significant step closer to predicting the onset of Alzheimer's disease through a straightforward blood test. Researchers found they could use blood samples to create a biological ‘clock’ capable of estimating when a person might begin experiencing symptoms even years before any memory loss or cognitive decline appears.

If confirmed in larger trials, the breakthrough could change how the disease is detected and treated potentially allowing doctors to intervene years before memory loss begins.

A blood test that predicts Alzheimer’s onset
Researchers have identified an abnormal form of a protein called tau that circulates in the blood long before symptoms appear.

The protein, known as p-tau217, builds up in the brains of people who go on to develop Alzheimer’s. By measuring levels of this protein through a blood draw, scientists were able to estimate when symptoms might start.

In the study, which involved more than 600 people aged between 62 and 78 who showed no cognitive impairment, researchers used blood test results to model the likely age at which Alzheimer’s symptoms would emerge.

Using this data, researchers built a predictive model that could estimate the likely age of symptom onset with an uncertainty window of around three to four years. Notably, the study found that the older a person was at the time of testing, the sooner their symptoms were likely to emerge.

Why early detection of Alzheimer’s matters
Alzheimer’s is a neurodegenerative disease that gradually damages memory and thinking skills. By the time symptoms such as memory loss appear, brain changes have often been underway for years.

Detecting Alzheimer’s before symptoms develop is considered crucial because treatments are more likely to work in the early stages.

Abnormal tau proteins can form tangled fibres in the brain, disrupting communication between nerve cells. Brain imaging tests can detect these tangles, and earlier research has suggested they may help predict symptom onset.

However, imaging scans and spinal fluid tests are expensive, invasive and not widely accessible.

Cheaper and more accessible than brain scans

The researchers say blood testing could offer a simpler alternative.

“Our work shows the feasibility of using blood tests, which are substantially cheaper and more accessible than brain imaging scans or spinal fluid tests, for predicting the onset of Alzheimer’s symptoms,” said the study’s lead author, Suzanne Schindler, a neurologist at Washington University School of Medicine in St. Louis, Missouri, United States.

Blood tests are already increasingly used to detect biological signs of Alzheimer’s, but this study goes a step further by attempting to estimate when symptoms may appear.

Interestingly, the researchers found that the older a person was, the sooner symptoms were likely to develop if the protein was present.Alzheimer