Association between tau deposition and antecedent amyloid-β accumulation rates in normal and early symptomatic individuals

A long-term goal of our field is to determine the sequence of pathological events, which ultimately lead to cognitive decline and dementia. In this study, we first assessed the patterns of brain tau tangle accumulation (measured with the positron emission tomography tracer ¹⁸F-AV-1451) associated with well-established Alzheimer's disease factors in a cohort including cognitively healthy elderly individuals and individuals at early symptomatic stages of Alzheimer's disease. We then explored highly associated patterns of greater ¹⁸F-AV-1451 binding and increased annualized change in cortical amyloid-β plaques measured as florbetapir positron emission tomography binding antecedent to ¹⁸F-AV-1451 positron emission tomography scans, and to what extent these multimodal pattern associations explained the variance in cognitive performance and clinical outcome measures, independently and jointly. We found that: (i) ¹⁸F-AV-1451 positron emission tomography retention was differentially associated with age, and cross-sectional florbetapir positron emission tomography retention, but not with years of education, gender, or APOE genotype; (ii) increased annualized change in florbetapir retention, antecedent to 18F-AV-1451 positron emission tomography scans, in the parieto-temporal and precuneus brain regions was associated with greater ¹⁸F-AV-1451 PET retention most prominently in the inferior temporal and inferior parietal regions in the full cohort, with florbetapir positive/negativeassociated variability; and (iii) this ¹⁸F-AV-1451 positron emission tomography retention pattern significantly explained the variance in cognitive performance and clinical outcome measures, independent of the associated antecedent increased annualized change in florbetapir positron emission tomography retention. These findings are in agreement with the pathology literature, which suggests that tau tangles but not amyloid-β plaques correlate with cognition and clinical symptoms. Furthermore, nonlocal associations linking increased amyloid-β accumulation rates with increased tau deposition are of great interest and support the idea that the amyloid-β pathology might have remote effects in disease pathology spread potentially via the brain's intrinsic connectivity networks.