2 Computerized Cognitive Practice Effects in Relation to Amyloid and Tau in Preclinical Alzheimer's Disease: Results from a Multi-Site Cohort

Abstract

Objective:

There is a need to identify scalable cognitive paradigms that are sensitive enough to relate to Alzheimer's disease biomarkers (amyloid and tau) in the preclinical stage. Here, we determine whether initial performance and practice effects on the memory-focused Computerized Cognitive Composite (C3) relate to demographic variables, amyloid status [abnormal (A+), normal (A-)], and regional tau in clinically unimpaired (CU) older adults.

Participants and Methods:

We examined pre-randomization data from CU older adults screened for the Anti-Amyloid Treatment in Asymptomatic Alzheimer's Disease (A4) study. We focused on participants who completed the C3 (n=3287), most of whom completed an alternate version of the C3 again approximately 51 days later (n=4141), as well as a subset of preclinical AD participants (i.e., A+ CU) who completed the C3 and tau PET imaging with [18]F-flortaucipir (initial C3: n=354; repeat C3: n=343). C3 initial performance and practice effects were examined in relation to amyloid status (A+, A-) and continuous regional tau burden.

Results:

Initial C3 performance was associated with amyloid status [B(SE) = -0.075 (0.021), p < 0.001] across all participants, as well as tau burden in the medial temporal lobe (MTL) [B (SE) = -0.728 (0.220), p = 0.001], inferior temporal (IT) cortex [B (SE) = -0.782 (0.264), p = 0.003], and inferior parietal (IP) cortex [B (SE) = -0.721 (0.281), p = 0.011] amongst preclinical AD individuals. Short-term practice effects were also associated with reduced tau burden in MTL [B (SE) = -0.471 (0.202), p = 0.020], IT [B (SE) = -0.640 (0.240), p = 0.008], and IP [B( SE) = - 0.584 (0.255), p = 0.023] amongst preclinical AD participants, but were not associated with amyloid status [B (SE) = -0.018 (0.020), p = 0.348]. Critically, these effects with tau were only detected when baseline performance was accounted for presumably due to opposing influence from both practice effects and regression to the mean effects.

Conclusions:

This is the first study to show that performance on a brief cognitive battery administered in a multisite context is associated with both amyloid and tau among CU older adults. These findings suggest that computerized assessments may be a cost-effective and scalable approach for early detection efforts. Further, diminished practice effects on memory-based measures are associated with elevated tau burden in preclinical AD, suggesting that high-frequency cognitive testing collected over a short follow-up period may provide additional insights regarding early disease processes than single assessments.