Cognitively healthy older adults with high levels of a biomarker called p-tau217 in their blood had an estimated 38% greater chance of developing early signs of dementia over five years, with the risk increasing to 78% over a decade, according to a new study, reports BritPanorama.
Lead study author Rachel Buckley, an associate professor of neurology at Harvard Medical School, stated, “What this tells me is that we really can use p-tau217 blood tests in future to be able to understand somebody’s individual risk of cognitive impairment.”
Traditionally, diagnosing Alzheimer’s required expensive and invasive procedures like PET scans or spinal taps. However, blood tests that measure levels of phosphorylated tau 217, or p-tau217, “strongly predict” the buildup of sticky beta-amyloid plaques in the brain, according to Buckley.
The amyloid plaques trigger inflammation and damage communication between neurons, accumulating in the brain decades before memory loss or cognitive decline — even in individuals in their 30s and 40s. As beta-amyloid levels rise, tangles of proteins called tau gather inside brain cells, causing neurons to collapse and die. In some cases of frontal lobe dementia, tau can accumulate without the presence of amyloid.
Not everyone with high levels of amyloid will progress to dementia, just as having tau in the brain does not necessarily dictate cognitive impairment later in life. Buckley noted, “However, if an early stage of tau is combined with very elevated levels of amyloid, amyloid appears to be the match that lights the fire for the spread of disease across the brain.” She explained that the p-tau217 test may indicate the point when amyloid starts to cause significant brain damage.
While blood tests are not currently recommended for cognitively healthy individuals, specialists can employ them for those exhibiting signs of mild cognitive impairment or advanced dementia. Buckley aims for the p-tau217 test to function similarly to tests assessing the risk of diabetes or heart attacks in the future.
How blood tests will be used
Insights from Alzheimer’s blood tests are invaluable, but they should not be the sole method of identifying disease risk. Alzheimer’s prevention researcher Dr. Richard Isaacson remarked, “Never would I order a p-tau217 test in isolation. Why? For one, it tells you only one small part of what is most often a complicated biological picture.” He recommended running multiple cognitive tests alongside p-tau217 assessments to ensure accurate results.
Isaacson also pointed out that ordering a single test increases the risk of a less meaningful result, such as a false positive, as various conditions can skew results. He utilizes p-tau217 and amyloid tests to monitor how patients respond to treatment and lifestyle changes rather than solely for diagnostic purposes.
These personalized lifestyle interventions, including improved diet and exercise, have shown promise in reducing amyloid and tau levels in patients committed to enhancing their health. The need for such multifaceted approaches in dementia care underscores the ongoing efforts to understand Alzheimer’s better.
Recent research indicates that as much as 45% of dementia cases can potentially be prevented through lifestyle interventions, including exercise and diet. Laura Nisenbaum, interim chief science officer at the Alzheimer’s Drug Discovery Foundation, emphasized that blood tests should complement cognitive assessments and help rule out other causes of impairment.
Blood tests need additional study
The study’s findings, set to be presented at the Alzheimer’s Association International Conference and published in JAMA, reanalyzed data from six observational and clinical trials involving nearly 2,700 older adults without cognitive decline symptoms. Participants underwent PET brain scans and p-tau217 tests, tracked for up to 21 years.
The study established a significant association between higher p-tau217 levels and cognitive impairment, with risk increasing over time. Results indicated that blood test data was informative regardless of a participant’s brain scan or genetic risk factors like APOE4, which can significantly elevate the likelihood of developing Alzheimer’s.
Despite the promising results, experts caution that these findings are in early stages and larger, more inclusive studies are required.
