Blood Test Forecasts Cognitive Impairment Risk in Healthy Older Adults

Researchers announced Wednesday that a blood test measuring p-tau217 levels can forecast the risk of cognitive impairment in healthy older adults years before symptoms appear. Individuals with the highest levels faced a 38 percent probability of impairment within five years and a 78 percent probability within a decade.

The results are based on data from 2,684 participants who were healthy at enrollment in long-running Alzheimer's studies that began as early as 2004.

Participants received blood tests and annual cognitive assessments, and 478 developed impairment during the follow-up period. The findings were published in JAMA and presented at the Alzheimer's Association International Conference in London. The test measures a form of the tau protein linked to amyloid plaques and tau tangles.

Dr. Reisa Sperling of the Mass General Brigham Neuroscience Institute, the study's senior author, said the marker identifies a tipping point in disease progression. "Wait and get tested when you can potentially do something about it," Sperling said.

In an accompanying JAMA editorial, Drs. Suzanne Schindler of Washington University in St. Louis and Jessica Langbaum of the Banner Alzheimer's Institute said people with a family history of the disease are already asking about the test.

Langbaum strongly discourages its use outside research settings until trials show that drugs can prevent or delay symptoms.