Tuesday, December 31, 2019

Subtle Cognitive Deficits May Precede Amyloid Accumulation in Alzheimer’s, Study Suggests

In the progression of Alzheimer’s disease (AD), subtle cognitive difficulties may develop prior to or alongside the early phases of amyloid accumulation, according to a study published Monday in Neurology. The findings challenge the hypothesis that amyloidosis (the buildup of amyloid proteins) comes first in the Alzheimer’s disease process.

Kelsey R. Thomas, Ph.D., of the VA San Diego Healthcare System and colleagues analyzed data from 747 people aged 55 to 90 without dementia who participated in the Alzheimer’s Disease Neuroimaging Initiative. The participants received PET imaging to determine amyloid levels at baseline, then each year over four years.

The researchers evaluated the cognitive abilities of the participants using memory, language, and attention tests at the beginning of the trial. In addition to examining the total score the participants earned on the cognitive tests, the researchers also gauged if the participants appeared to demonstrate errors in the processes used to complete the tasks. Based on these tests, the researchers divided the participants into three groups: those who were cognitively normal, those with mild cognitive impairment (MCI), and those with subtle cognitive difficulties.

Baseline amyloid levels did not statistically differ between the participants who were cognitively normal or had subtle cognitive difficulties, but those with subtle cognitive difficulties showed faster rates of amyloid accumulation over the four-year study. Additional analysis revealed that participants in the MCI and subtle cognitive difficulties groups had faster thinning of the entorhinal cortex (a brain region known to be impacted early in the progression of Alzheimer’s disease) relative to the cognitively normal group.

“[O]ur study demonstrated a method to successfully detect subtle differences in thinking and memory either before or during the phase when amyloid is accumulating at a faster rate,” Thomas said in a press statement. “This could lead to noninvasive screenings that may be able to detect very early who is at risk of developing Alzheimer's disease.”

In an editorial accompanying the study, Beth E. Snitz, Ph.D., and Adam M. Brickman, Ph.D., of the University of Pittsburgh wrote of the importance of cognitive tests in Alzheimer’s research: “Despite the recent emphasis on characterizing [Alzheimer’s disease] based on biomarker profiles alone, it is critical to emphasize that it is the cognitive deficits and associated functional impairment that are most problematic for patients and their families, and, as illustrated in the Thomas et al. study, highly predictive of the course of the disease. There is thus a great need to continue to focus on cognition, including the implementation and development of methods that push the boundaries of early detection.”

For related information, see the Psychiatric News article “Are Amyloid and Tau Good Biomarkers For Alzheimer’s Disease?

(Image: iStock/Ridofranz)

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