Alzheimer's preclinical stage reveals three distinct cognitive decline paths

New analysis of 1,629 older adults tracked for up to seven years identifies three cognitive trajectories in preclinical Alzheimer's: stable, slow decline, and fast decline, with about 70% remaining stable over about six years. Baseline biomarkers—higher p-tau217, greater tau burden on brain scans, and smaller hippocampus—predicted faster decline, while the APOE ε4 allele also increased risk. Amyloid presence mattered but was a weaker predictor than tau and brain structure. The findings suggest clinical trials in preclinical Alzheimer's should target likely decliners to improve efficiency, since enrolling many stable individuals can dilute a treatment effect. Predictions are probabilistic, not exact, and researchers call for more biomarkers and refined models to guide trials and prognosis.