In the near future, doctors might be able to predict when a patient will develop Alzheimer’s disease using a straightforward blood test.

A team of researchers from Washington University in St. Louis observed over 500 adults in their 60s and 70s over a period of up to seven years. They focused on measuring the levels of a specific protein in the blood that is associated with this debilitating condition.

The data collected was then used to construct a predictive model that estimates when symptoms may appear, with an accuracy of three to four years.

In their study, scientists monitored the levels of a misfolded protein known as p-tau217 found in the blood, which has been linked to Alzheimer’s, the most prevalent form of dementia.

Currently, this blood test is available solely for clinical trials. However, the research team aims to eventually make it accessible to patients, particularly those with a higher risk due to genetic factors, enabling them to devise strategies to prevent or slow the progression of the disease.

Dr. Suzanne Schindler, the study’s lead clinical neurologist, stated, “Our research demonstrates the potential of using blood tests, which are significantly more affordable and accessible than brain imaging scans or spinal fluid tests, to predict the onset of Alzheimer’s symptoms.”

The team hopes that the research could also help with the development of treatments that could prevent Alzheimer’s disease by helping to identify the characteristics of participants whose symptoms slowed after having the test. 

About seven million Americans are already living with Alzheimer’s disease, the most common form of dementia, but this number is expected to almost double by 2050.

Scientists say they have developed a new blood test that could help to diagnose Alzheimer’s disease (stock image) 

It is not clear what causes the disease, but a large body of research suggests it may be linked to a build-up of two misfolded proteins — amyloid and tau — that could interfere with communications between nerve cells.

These proteins normally form the structure of nerve cells, but can also form ‘clumps’ or ‘tangles’ in the brain that may affect other neurons.

Previous studies have shown that their levels rise gradually in patients at risk from the disease due to age or family history, which scientists said meant they could be used to estimate when the neurodegenerative condition may occur.

For the study, published in the journal Nature Medicine, researchers analyzed data on participants from two studies completed over the last two years. One was led by the University of Washington in St Louis team and the other by scientists at the Northern California Institute for Research.

The St Louis cohort included 258 individuals who had their blood p-tau217 levels tested at least three times over 6.5 years. Overall, participants were 68 years old on average and eight percent had cognitive impairment, or a decline in mental function.

In the California cohort, 345 individuals had the p-tau217 levels in their blood tested at least three times over a period of 4.5 years. Overall, the participants were 73 years old on average and nearly 50 percent had cognitive impairment.

Jana Nelson was 50 when diagnosed with early onset dementia, following severe personality changes and a sharp cognitive decline that left her unable to solve simple math problems or name colors. There is no suggestion that she developed this complication because of cannabis

During the study period, a total of 79 participants across both studies were diagnosed with Alzheimer’s disease.

Data on the p-tau217 levels and when Alzheimer’s symptoms began was analyzed to allow researchers to build a model predicting the onset of the disease.

Researchers said, however, that they were only able to predict the age to within three to four years. They warned the study was based on a small sample size, and urged other scientists to also analyze p-tau217 levels to allow them to expand the dataset.

Dr Kellen Petersen, a neurologist who was also involved in the study, said: ‘Amyloid and tau levels are similar to tree rings, if we know how many rings a tree has, we know how many years old it is.

‘It turns out that amyloid and tau also accumulate in a consistent pattern and the age they become positive strongly predicts when someone is going to develop Alzheimer’s symptoms. 

‘We found this is also true of plasma p-tau217, which reflects both amyloid and tau levels.’