June 07, 2019
By Reuters Staff
NEW YORK (Reuters Health) - Increasing amyloid-beta (A-beta) plaques followed by accumulation of tau neurofibrillary tangles is strongly associated with cognitive decline over a seven-year period, according to new findings.
"Altogether, our findings indicate that A-beta PET measures have a delayed and indirect, tau-mediated association with cognition," Dr. Bernard J. Hanseeuw of Massachusetts General Hospital in Boston and colleagues conclude in JAMA Neurology, online June 3.
A-beta accumulation is believed to occur before tau pathology, with the former accelerating the latter, but the temporal sequence of A-beta and tau-tangle accumulation has not been established, the authors note.
To investigate, they analyzed PET data on 60 men and women who participated in the Harvard Aging Brain Study and underwent a median of three amyloid-beta scans between 2010 and 2017 and two tau scans between 2013 and 2017. The patients also had annual cognitive evaluations with the Preclinical Alzheimer Cognitive Composite.
At the outset of the study, 17 patients had a high A-beta burden. Increases in A-beta were linked to subsequent tau changes, which in turn were associated with cognitive changes. The six study participants who progressed to mild cognitive impairment (MCI) over the study period had the greatest changes in tau.
None of the study participants exhibited the full sequence during the study period, indicating that progression of sub-threshold A-beta to MCI takes longer than seven years, the authors note.
The findings suggest that stopping the accumulation of tau could ward off cognitive decline, they add.
"These findings highlight the importance of repeated tau-PET observations to track disease progression and the importance of repeated amyloid-PET observations to detect the earliest AD pathologic change," they conclude.
JAMA Neurol 2019.
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