The cross-sectional studies have generally found that females show significantly better memory performance than males among those diagnosed as cognitively normal or MCI or among those with mild to moderate levels of AD biomarkers in the brain (i.e., hippocampal volume [16], Aβ [8, 11], tau [8, 9], and brain glucose metabolism [17]), whereas this sex difference was absent among patients with AD demntia or when biomarker levels were high [8, 9, 11, 16, 18, 19]. The gene discussed is MAPT; the disease is Alzheimer disease.