Decline in Cognitive Function over 18 Months in Healthy Older Adults with High Amyloid-β

We aimed to characterize the nature and magnitude of cognitive decline in a group of healthy older adults with high and low levels of amyloid-beta (A beta) and who were APOE epsilon 4 carriers and non-carriers. Healthy older adults underwent positron emission tomography neuroimaging for A beta, APOE genotyping, and cognitive and clinical assessment as part of their baseline assessment in the Australian Imaging, Biomarker, and Lifestyle study. Cognitive function and clinical ratings were reassessed 18 months later. Linear mixed model analyses adjusted for baseline cognitive function indicated that relative to healthy older adults with low A beta, healthy older adults with high A beta showed greater decline in episodic memory and language at 18 months. No decline on any measure of executive function, attention, or clinical rating was observed for healthy older adults with high A beta levels. Compared to non-carriers, APOE epsilon 4 carriers showed a greater decline only on the task of visual memory at the 18 month assessment. Importantly though, no interaction between APOE epsilon 4 and A beta was observed on any measure of cognitive function. The results of this study suggest that high A beta load was associated with greater decline in episodic memory and language, that the magnitude of this decline was moderate and equivalent across both domains, and that APOE epsilon 4 carriage did not moderate the relationship between A beta and decline in memory and language functions.