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An elevated level of a certain protein in the blood may be associated with memory decline years later, even if the person shows no noticeable cognitive problems at the initial examination. Researchers found such a link by comparing blood tests and cognitive test results of 1170 participants with a six-year interval.
This was reported by ScienceAlert.
Researchers at the Miller School of Medicine at the University of Miami investigated biological changes that may precede memory decline and other cognitive impairments. The study’s results were published in the journal Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring.
The most notable association with later memory decline was found for the protein p-tau181. It belongs to biomarkers studied in connection with Alzheimer’s disease. In people with that disease, abnormal accumulation of the tau protein occurs in the brain.
The study included 1170 people with a mean age of 73 years. In 2016 they gave blood and took cognitive tests. Six years later, in 2022, participants repeated the tests, but no new blood draws were performed at that follow-up.
Researchers assessed memory, language skills, executive function, and the ability to perceive and process visuospatial information. The blood analysis covered four biomarkers linked to different brain processes.
At baseline, p-tau181 levels showed no noticeable association with memory test results. However, six years later higher initial levels of this protein were associated with worse performance on memory tests and overall cognitive abilities.
Cognitive neurologist Deirdre O’Shea explained that a blood test can detect biological changes that have not yet affected performance on test tasks. At the same time, the observed association does not mean that a single marker can precisely predict an individual’s memory status.
Another important biomarker was GFAP — a protein associated with astrocytes, cells that perform supportive functions in the brain. Its baseline level was associated with memory, executive function, and overall cognitive performance six years later.
The scientists also examined NfL and the Aβ42/40 ratio. NfL can enter the blood when nerve fibers are damaged. The Aβ42/40 ratio is used as a biomarker for processes related to beta-amyloid accumulation — another characteristic feature of Alzheimer’s disease.
At the initial assessment, the strongest associations with current cognitive measures, including memory and executive function, were found for NfL and GFAP. However, at the follow-up testing p-tau181 and GFAP drew particular attention.
Most participants had no cognitive impairment at baseline, although some had already been diagnosed with mild cognitive impairment or dementia. The main patterns held when the researchers separately analyzed the results of people with normal cognitive measures at the start of observation.
O’Shea noted that biomarker levels should not be reduced to just two categories — “positive” or “negative.” The researchers considered the full range of values and compared them with individual measures of memory and other cognitive abilities to detect associations that might be missed by a simplified approach.
The results do not mean that a blood test can establish a dementia diagnosis in advance. The study concerned the association between biomarkers and subsequent cognitive measures, not the precise prediction of who will develop Alzheimer’s disease.
The scientists suggest that combining p-tau181 and GFAP measurements could in the future help assess the risk of cognitive decline. However, additional research is needed before such an approach can be applied.
Next, the authors plan to observe participants for a longer period, repeatedly perform blood tests and cognitive assessments, and compare biomarker levels with confirmed cases of Alzheimer’s disease and other forms of dementia.
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