MAPT and Alzheimer disease: On the other hand, well-powered case-control AD dementia GWAS focus on dementia diagnosis (the final outcome of AD progression) and does not account for individual-level AD endophenotype (e.g., Aβ, tau, cognitive decline) variability, lacking the resolution to localize the cell-type-specific genetic association to a specific AD endophenotype (“how”) at a specific stage of disease progression (“when”).