New Delhi: A simple blood test may now help predict when a person will begin to show symptoms of Alzheimer’s disease. A new study by researchers at Washington University School of Medicine in St. Louis, published in Nature Medicine, shows that a protein found in the blood can help estimate the age at which memory decline linked to Alzheimer’s may begin, within a margin of three to four years.
Scientists say this approach could help identify the right time for clinical trials aimed at delaying the disease.
Alzheimer’s is a brain disorder that slowly affects memory, thinking and behaviour. It develops when two proteins—amyloid and tau—build up in the brain. These proteins form clumps and tangles that damage brain cells.
In the early stages, a person may forget recent conversations or misplace items. As the disease progresses, daily activities such as cooking, managing money or recognising family members can become difficult. There is no cure for Alzheimer’s disease yet. But the Food and Drug Administration has approved some medicines that can help manage symptoms at different stages of the illness.
One group of medicines, called cholinesterase inhibitors, helps boost levels of a brain chemical called acetylcholine, which is important for memory and thinking. Another drug, memantine, works on a different brain chemical called glutamate, which also plays a role in learning and memory. Brexpiprazole is a medicine used to treat agitation—such as restlessness or aggression—in people with Alzheimer’s disease.
These medicines are not recommended for mild cognitive impairment, which involves small but noticeable memory problems that are not severe enough to be dementia. Overall, treatment options are still limited, and the medicines work differently for different people.
The new research published in Nature Medicine focuses on a specific form of tau called p-tau217. This protein can be detected in a blood sample. Higher levels of p-tau217 are linked to the buildup of amyloid and tau in the brain, which are key signs of Alzheimer’s.
Researchers describe their model as a “clock” because it tracks the biological progression of the disease. This clock model measures how much p-tau217 has accumulated in the blood over time. The more that has built up, the further a person may be along the path toward developing symptoms of Alzheimer’s.
“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,” Suzanne E. Schindler, an associate professor in the Washington University Medicine Department of Neurology and senior author of the study said.
She also said these clock models may allow clinical trials of potentially preventive treatments to be performed within a shorter time.
“In the near term, these models will accelerate our research and clinical trials,” she said. “Eventually, the goal is to be able to tell individual patients when they are likely to develop symptoms, which will help them and their doctors develop a plan to prevent or slow symptoms.”
Why are doctors cautious?
The team studied data from more than 600 older adults and participants were tracked over several years. The researchers found that the blood-based model could predict the likelihood of symptoms being developed.
The older a person was, the sooner symptoms would appear, the researchers found. For example, if a person had elevated p-tau217 levels at age 60, symptoms often appeared about 20 years later. If levels first rose at age 80, symptoms appeared in roughly 11 years. This suggests age may affect how quickly symptoms follow biological changes in the brain.
Currently, Alzheimer’s-related changes are detected using amyloid PET scans—a type of medical brain imaging—or Cerebrospinal fluid (CSF) tests, which are used to help diagnose a wide variety of diseases and conditions affecting the central nervous system. But these can be costly or invasive.
Dr Madhukar Bhardwaj, Director & HOD, Neurology, at Aakash Healthcare said, “By the time many patients are diagnosed, the disease is already at an advanced stage,” he said.
He called blood biomarkers such as p-tau217 “an important step forward” in screening, but cautioned that “these tests are supportive tools, not absolute diagnostic replacements”. A normal result does not fully rule out future disease, he said.
The authors of the study also say that the model could help improve clinical trials.
Many drug trials fail because treatment begins after brain damage has already occurred. If researchers can identify people who are likely to develop symptoms within a set period, they can test preventive treatments earlier.
Dr Nitin K. Sethi, chairman, neurosciences, at PSRI Hospital, said early diagnosis is “potentially a game changer”.
However, he added that such therapies are not widely available in India and that currently used medicines like donepezil and memantine only slow memory decline marginally.
Dr Anshu Rohtagi, vice chairman, neurology, at Sir Ganga Ram Hospital, said this test does away with the need for amyloid PET and CSF examination in many cases and helps identify early Alzheimer’s patients for disease-modifying treatment. However, she also agrees that false positive tests must be interpreted carefully.
(Edited by Viny Mishra)