Buckley RF, et al. - The associations between subjective cognitive decline (SCD) and global β-amyloid (Aβ) and tau burdens in regions of interest in clinically healthy older adults were examined. In the medial temporal lobe, the subjective cognitive decline was indicative of accumulation of early tauopathy, particularly in the entorhinal cortex, and to a lesser extent, elevated global levels of Aβ. The authors proposed multiple underlying pathways that motivated SCD that did not necessarily interact to influence SCD endorsement. Fundamentally, when assessing SCD in clinically healthy older adults, multiple biological factors ought to be considered.

• The authors performed this imaging substudy of the Harvard Aging Brain Study.
• They included 133 clinically healthy older participants (Clinical Dementia Rating Scale global scores of 0).
• The participants underwent cross-sectional flortaucipir F 18 (previously known as AV 1451, T807) positron emission tomography (FTP-PET) imaging for tau and Pittsburgh compound B carbon 11-labeled PET (PiB-PET) imaging for Aβ.
• They identified the following 2 regions for tau burden: the entorhinal cortex, which exhibited early signs of tauopathy, and the inferior temporal region, which was more closely associated with AD-related pathologic mechanisms.
• They collected data from June 11, 2012, through April 7, 2016.

• 75 (56.3%) were women and 58 (43.6%) were men among the 133 participants; mean (SD) age was 76 (6.9) years (range, 55-90 years).
• 39 participants (29.3%) showed a high Aβ burden.
• Greater SCD was correlated with increasing entorhinal cortical tau burden (β = 0.35; 95% CI, 0.19-.52; P < .001) and Aβ burden (β = 0.24; 95% CI, 0.08-.40; P = .005), but not inferior temporal tau burden (β = 0.10; 95% CI, -0.08 to 0.28; P = .27).
• After accounting for Aβ burden, this association between entorhinal cortical tau burden and SCD was largely unchanged (β = 0.36; 95% CI, 0.15-.58; P = .001), and no interaction influenced SCD (β = -0.36; 95% CI, -0.34 to 0.09; P = .25).
• Moreover, an exploratory post hoc whole-brain analysis demonstrated that SCD was predominantly associated with greater tau burden in the entorhinal cortex.