Higher Amyloid and Tau Burden Is Associated With Faster Decline on a Digital Cognitive Test

Objective: A 2-min digital clock-drawing test (DCTclock) captures more granular features of the clock-drawing process than the pencil-and-paper clock-drawing test, revealing more subtle deficits at the preclinical stage of Alzheimer's disease (AD). A previous cross-sectional study demonstrated that worse DCTclock performance was associated with higher Aβ and tau burden in older cognitively normal (CN) participants. This study investigates whether longitudinal changes in DCTclock performance are associated with amyloid-β (Aβ) and tau burden in preclinical AD. Methods: A total of 219 CN participants completed baseline and follow-up DCTclock assessments, baseline Aβ ([11C]PiB) and tau ([18F]Flortaucipir) PET imaging. Global Aβ and regional tau burden were estimated. Linear mixed models examined associations between longitudinal DCTclock and (1) Aβ, (2) tau, and (3) Aβ and tau burden, adjusted for age, sex, and education. Cognitive domain-specific performance and fine-grained features of DCTclock were analyzed. Results: Elevated baseline Aβ or tau was most strongly associated with accelerated decline in DCTclock performance, particularly in the Information Processing cognitive domain, with stronger associations noted for tau burden. The associations were driven by pen-stroke latency-related features. Participants without elevated Aβ or tau burden demonstrated improved performance in these latency features, suggesting practice effects. Interpretation: Longitudinal declines in DCTclock performance, especially in Information Processing involving speed and executive function, were linked to early Aβ and tau burden in preclinical AD. These findings highlight the potential of digital cognitive assessment tools for tracking disease progression and assessing therapeutic efficacy in clinical trials.