Tau pathology and cognitive reserve in Alzheimer's disease

Cognitive reserve (CR) is defined as the ability to maintain functionality despite accumulating pathology. Education has been used as a proxy for CR. For example, by using positron emission tomography imaging, higher educated Alzheimer's disease (AD) patients presented increased amyloid β pathology than lower educated patients despite equal symptomatology. Whether similar associations exist for in vivo tau pathology remains elusive. We utilized [18F]AV-1451 positron emission tomography imaging to examine whether high-educated AD patients (n = 12) present more severe tau pathology compared with low-educated patients (n = 12) despite equal clinical severity in regions of interest corresponding to the pathologic disease stages defined by Braak & Braak. We report tau pathology in advanced Braak stages associated with parietal and frontal regions in high-educated AD patients, whereas in low-educated AD patients tau accumulation is still confined to lower Braak stages associated with temporal and cingulate regions. Highly educated AD patients seem to be able to tolerate more tau tangle pathology than lower educated patients with comparable cognitive impairment supporting the cognitive reserve hypothesis.