Blood Test May Identify Alzheimer's Risk Years Before Symptoms Appear, Research Shows

Higher levels of plasma phosphorylated tau 217, or p-tau217, a biomarker associated with Alzheimer's-related changes in the brain, were linked with a higher chance of future cognitive decline in older adults not yet showing signs of impairment, the study found.

Audrey Simons

Published: 7/15/2026, 10:54:21 PM EDT

Blood Test May Identify Alzheimer's Risk Years Before Symptoms Appear, Research Shows — A picture of a human brain taken by a positron emission tomography scanner, also called PET scan. (Fred Tanneau/AFP via Getty Images)

A blood test that measures a protein linked to Alzheimer's disease may help identify older adults who are at an increased risk of cognitive impairment years before symptoms ever appear, according to research published on Tuesday in the peer-reviewed medical journal JAMA.

The findings were also presented at the Alzheimer's Association International Conference in London on Wednesday.

Researchers from Mass General Brigham and other collaborating institutions found that higher levels of plasma phosphorylated tau 217, or p-tau217, a biomarker associated with Alzheimer's-related changes in the brain, were linked with a higher chance of future cognitive decline in older adults not yet showing signs of impairment.

The study examined data from nearly 2,700 unimpaired participants from multiple long-term studies, and found that cognitively healthy older adults with very high levels of p-tau217 had about a 38 percent likelihood of developing mild cognitive impairment or dementia within five years. The risk rose to approximately 78 percent over 10 years.

In a statement, Ron Brookmeyer, a professor of biostatistics at UCLA's Fielding School of Public Health and a co-author of the study, said the findings could help identify people who may benefit from future treatments.

"Identifying who is at high risk is important," Brookmeyer said. "Treatments currently under development may work better in slowing or preventing dementia if started early before the onset of symptoms."

There is currently no known cure for Alzheimer's, which is the most common cause of dementia, accounting for roughly 60 to 80 percent of all cases, according to the Alzheimer's Association. However, some treatments may help alter the progression of the disease.

The study's senior author, Dr. Reisa Sperling, a neurologist with the Mass General Brigham Neuroscience Institute, noted that the blood test is not currently recommended for those who are asymptomatic.

"We do not yet have disease-modifying treatments for people who find out they are at high risk for developing cognitive impairment due to Alzheimer’s disease," she said in a press release.

Instead, Sperling said current medical recommendations remain the same, which include getting regular exercise, eating a healthy diet, and prioritizing good sleep and overall wellness.

She added that the preventive care landscape could always shift if ongoing trials show that disease-modifying therapies are effective.

"In the future, these tests could help identify those who might benefit most from these treatments," she said. "Our long-term goal is to get us to where cholesterol testing is in predicting your risk of a heart attack."