APOE and Cognitive impairment: Our primary objectives were to (1) investigate the association between α‐syn pathology and regional brain glucose metabolism and the extent to which it is independent of apolipoprotein E (APOE) status and AD pathology, (2) examine the interactions between SAA positivity and established biomarkers of AD on FDG PET metabolism, and (3) determine whether hypometabolism might serve as a mechanistic link between α‐syn pathology and cognitive impairment within the AD spectrum.