Study evaluates biomarker criteria for assessing Alzheimer’s risk
2021 MAY 10 (NewsRx) -- By a
Researchers have focused primarily on three such biomarkers. Two are Alzheimer’s-related proteins, amyloid and tau. Amyloid forms clumps in brains, and tau forms skeins of filaments called neurofibrillary tangles. Both can be detected in cerebral spinal fluid or by specialized positron emission tomography (PET) scans. The third marker, brain atrophy, can be seen with CT or MRI scans.
To guide researchers, the
A new study by researchers in
“We used autopsy data to approximate AT(N) biomarker categories from our well-characterized sample, and looked at dementia rates for people in each category,” said Dr.
The paper appears in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association. The title is “Theoretical impact of the AT(N) framework on dementia using a community autopsy sample.”
In the study, researchers used data collected by the Adult Changes in Thought study. The ACT study started in the 1990s. ACT has followed more than 5,500 older volunteers to identify new cases of dementia. About a third of the volunteers allowed their brains to be studied after death.
Because Alzheimer’s progresses slowly, the ACT participant autopsy results for amyloid, tau, and neurodegeneration were used to approximate AT(N) classification five years before death. The researchers considered evaluations over the five years before death to see whether the proxy AT(N) categorization at that time would predict dementia development in those five years.
The AT(N) framework uses eight different biomarker profiles, ranging from none of the biomarkers, designated
The researchers found that 67% of those with the proxy A+T+(N)+ profile developed dementia in the next five years. But 33% did not.
“A+T+(N)+ is supposed to be the highest risk group,” Crane noted. “They have high levels of amyloid, high levels of tau, and have atrophy. Even in that group, a third never developed dementia.”
The findings, if validated with AT(N) biomarkers, suggest that any drug trial using the AT(N) framework will require many more participants to be screened to enroll enough people to achieve statistically solid results, Crane noted. Because PET scans used to detect amyloid and tau cost thousands of dollars, such studies would be even more expensive.
Larson noted, “This paper is important and was possible because of the longtime commitments of ACT subjects and their families, an enduring partnership between Kaiser Permanente Washington (formerly
Dr.
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