How does p-tau217 affect your brain health?
The JAMA study explored the preclinical or pre-impairment stage of Alzheimer’s disease. During this first stage, tau tangles and amyloid plaques start to form. But these changes don’t yet affect your memory or thinking.
For the JAMA study, a group of researchers looked at p-tau217 levels in close to 2,700 cognitively healthy adults aged 60 and older. The adults participated in six different research studies dating back to 2004. The study found that participants with very high levels of p-tau217 (defined as more than twice the average level) had:
- 38% absolute risk of cognitive impairment over the next 5 years
- 78% absolute risk of cognitive impairment over the next 10 years
In comparison, people with slightly elevated p-tau217 levels (defined as just above average) had:
- 15% chance of cognitive impairment over the next 5 years
- 45% chance of cognitive impairment over the next 10 years
“Absolute risk indicates the likelihood of actually progressing to cognitive impairment over set time frames when factoring in certain parameters,” says Dr. Buckley. “Our study considered p-tau217 levels along with a person’s age, biological sex, and education levels. Future studies will also include health factors or comorbidities, such as high blood pressure and diabetes, which can affect brain health.”
Researchers also included results from positron emission tomography (PET) scans. These brain imaging scans, along with lumbar punctures (spinal taps) to measure tau protein and amyloid-beta-42 peptide, are currently the gold standard for diagnosing Alzheimer’s disease. But these tests are more invasive than a blood test. And they don’t typically take place until a person shows signs of cognitive impairment.
“In our study, the blood test was more informative and predictive of Alzheimer’s disease risk than PET scans and known genetic risk factors,” says Dr. Buckley.
Should you take an Alzheimer’s disease blood test?
Since 2025, the U.S. Food and Drug Administration (FDA) has approved four biomarker blood tests for Alzheimer’s disease. The most recently approved test, Elecsys®, measures only p-tau217 levels in plasma, the liquid part of blood. But the Alzheimer’s Association and other experts advise against testing if you don’t have symptoms and aren’t participating in a research study.
FDA-approved tests require a doctor’s prescription. But Medicare and private health insurers are unlikely to cover the costs, which can range from $200 to $1,500, if you don’t have symptoms. In fact, Medicare doesn’t even cover the costs for patients with symptoms. The bipartisan Alzheimer’s Screening and Prevention (ASAP) Act seeks to change that. However, the legislation, introduced in 2025, is still awaiting congressional approval.
While you can purchase at-home biomarker tests online, their accuracy and reliability vary. “I don’t recommend online tests because the results can be confusing and alarming without the right support from a knowledgeable health care provider or research study,” says Dr. Sperling.
Source: www.massgeneralbrigham.org
