Blood Test Could Tell You When Alzheimer’s Symptoms Will Start

Researchers say they are getting closer to developing a kind of “countdown clock” for Alzheimer’s disease. A study published Thursday in the journal Nature Medicine found that a blood test measuring a protein called p-tau217 may help estimate when a person is likely to develop symptoms, with an average margin of about three to four years, according to the Washington Post.

Blood tests that reflect the buildup of amyloid plaques in the brain are already used to help diagnose people with memory problems. This new work, based on data from about 600 older adults, moves the science toward predicting the disease before symptoms appear—at least in research settings. Higher levels of p-tau217 were linked to a faster onset of symptoms, and age played a role: a spike in the protein at age 60 was associated with symptoms roughly 20 years later, compared with about 11 years if levels rose at age 80.

The model is not yet accurate enough for routine clinical use. Researchers say it could be improved by tracking additional blood markers and should not be used on healthy people outside of studies. Still, specialists say it could soon change how clinical trials are conducted by identifying symptom-free volunteers who are most likely to decline in the near future—an important step if experimental drugs are most effective before noticeable memory loss.

“Ultimately, the goal is to be able to tell individual patients when they are likely to develop symptoms,” senior author Dr. Suzanne Schindler of Washington University said in a statement. Experts not involved in the study describe the approach as promising but say it needs to be confirmed in larger, more diverse populations and will only be truly useful if early treatments that balance risks and benefits prove effective.

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