A Blood Test That Hints at Alzheimer's Risk Years Ahead: What It Means for You Today
Saturday, October 31, 2026
Happy Halloween. This week brought one of the clearest looks yet at what an Alzheimer's blood test can and can't tell a healthy person about the future.
What happened. Researchers led by Mass General Brigham pooled data from six studies in North America, Japan and Australia: 2,684 older adults who had no memory or thinking problems when they joined. Everyone gave a blood sample that was tested for p-tau217, a protein linked to Alzheimer's changes in the brain, and was then followed with yearly check-ups. Some had been followed since 2004. About 478 went on to develop cognitive impairment (Mass General Brigham via ScienceDaily, Oct 30, 2026; journal article, JAMA).
What they found. Higher p-tau217 levels were strongly linked to a higher chance of later problems. People with very high levels had an estimated 38% chance of developing cognitive impairment within five years, rising to an estimated 78% within ten. The researchers stress the ten-year figure rests on much less data, so it's less certain. The blood marker added information beyond amyloid brain scans and beyond the best-known Alzheimer's risk gene, APOE4.
What it can't tell us. The people studied may not represent everyone, and the results are estimates for groups over limited time periods, not a lifetime forecast for any one person. Most important, the researchers say these blood tests are not currently recommended for people without symptoms, because there's no proven treatment yet to prevent decline in healthy people found to be at high risk. Senior author Dr. Reisa Sperling said that today the advice would be the same whatever the result: exercise regularly, eat a healthy diet, and prioritize sleep and overall wellness. Right now, these tests mainly help find volunteers for prevention trials. For more, see our guides to Alzheimer's blood tests and prevention trials.
Try this today: use tonight's extra hour for sleep
The advice from this study's own researchers starts with basics anyone can do, and sleep is one of them. In most of the U.S., clocks go back one hour at 2 a.m. tomorrow, Sunday, November 1. Instead of staying up later, try going to bed at your usual time and enjoying the extra hour of rest. If you care for someone with dementia, the time change can throw off routines: keep meals and bedtime on the new clock (ask the pharmacist if you are unsure how to time medicines), open the curtains for morning light, and expect a few unsettled evenings. Our guide to sundowning has more ideas, and sleep and brain health explains why rest matters. If you're worried about your own memory, talk to your doctor about whether any test makes sense for you.
Thanks for reading, and take care of yourself today.
Read the original study: https://doi.org/10.1001/jama.2026.12556
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