Using memory recall response time on digital cognitive testing to detect subtle cognitive changes among cognitively unimpaired older adults.

introductionWe investigated whether memory recall response time (RT) on remote digital testing reflects decrements in memory function linked to Alzheimer's disease (AD) biomarkers.

methodsOne hundred seventy-five cognitively unimpaired participants (age = 74.21 ± 8.33; 66.9% female) completed daily associative memory tests over 7 days. We examined how RT changed with repeated learning and how this related to accuracy. In a positron emission tomography-imaged subsample (n = 150), linear regression evaluated associations between mean RT across Days 1 to 3 and Days 5 to 7 and cortical amyloid and medial temporal and neocortical tau.

resultsRT for correct items progressively decreased, with a stronger RT-accuracy association observed on later learning days than at baseline. Moreover, even after accuracy plateaued, RT continued improving. Slower RT was associated with higher medial temporal tau but not with amyloid burden. DISCUSSION: Recall RT provides additional insight into AD-related learning decrements beyond accuracy alone. Slower RT in the memory recall task possibly reflects tau burden. HIGHLIGHTS: We examined recall response time (RT) changes over 7 days of repeated digital learning tasks. RT reveals learning-related changes even after accuracy plateaus. RT correlates with medial temporal tau and is moderated by age for neocortical tau. Digital RT data provide insights beyond accuracy, detecting subtle cognitive changes. RT may serve as a novel digital marker for preclinical Alzheimer's disease.