To test our hypothesis that microglial markers protect against future AD-related changes in the presence of amyloid or tau, we studied two sub-groups based on previously established cut-offs for amyloid- and tau-PET positivity12,13: specifically 121 subjects with evidence of amyloid pathology (A+) and 64 with additional evidence of tau pathological changes (T+). This evidence concerns the gene MAPT and Alzheimer disease.