Abstract
BACKGROUND AND OBJECTIVES: Although amyloid positron emission tomography (PET) and Cerebrospinal fluid (CSF) biomarkers remain the standard for confirming Alzheimer's disease (AD) pathology, their use is impractical for screening or routine prognostic assessment. Plasma phosphorylated tau 217 (p-tau217), subjective cognitive concerns, and computerized cognitive testing are non-invasive, scalable, and feasible to implement in large populations. We tested whether these measures independently predict the onset of cognitive impairment and whether combining them improves prognostic accuracy. METHODS: We analyzed 1,071 cognitively unimpaired adults aged 65-85 years from the Anti-Amyloid Treatment in Asymptomatic Alzheimer's Disease (A4) trial (amyloid-positive; solanezumab or placebo arms) and the parallel Longitudinal Evaluation of Amyloid Risk and Neurodegeneration (LEARN) cohort (amyloid-negative). At baseline, participants completed plasma p-tau217 measurement, the Cognitive Function Index (CFI), and the Cogstate Computerized Battery (CCB). Over 240 weeks of follow-up, incident impairment was defined as conversion from a Global Clinical Dementia Rating Score (CDR-GS) of 0 to 0.5 or higher. The predictive value of each measure for subsequent decline was examined after adjustment for demographic and genetic covariates. RESULTS: During the follow-up, 365 of 1,071 participants (34.1%) developed cognitive impairment. Higher plasma p-tau217 (per-standard-deviation increase) was associated with higher odds of converting to CDR-GS>0 across all cohorts: A4-Placebo (HR=1.56; 95% CI, 1.37-1.78), A4-Solanezumab (HR=1.46; 95% CI, 1.29-1.65), LEARN (HR=1.25; 95% CI, 1.05-1.48). Similarly, higher CFI predicted incident impairment: A4-Placebo (HR=1.59; 95% CI, 1.42-1.79), A4-Solanezumab (HR=1.67; 95% CI, 1.47-1.91), LEARN (HR=1.37; 95% CI, 1.12-1.68). Lower CCB also conferred higher risk: A4-Placebo (HR=0.76; 95% CI, 0.65-0.91), A4-Solanezumab (HR=0.73; 95% CI, 0.62-0.87), LEARN (HR=0.68; 95% CI, 0.53-0.87). In models including all three predictors, each remained independently associated with progression. CONCLUSION: Plasma p-tau217, subjective cognitive concerns, and computerized cognitive testing each independently predicted progression to cognitive impairment in cognitively unimpaired older adults. Together, these non-invasive and scalable measures provide practical tools for risk stratification years before clinical diagnosis. Combining biological, subjective, and digital markers may support earlier detection in clinical care and enhance efficiency in prevention trial enrollment.