67 Grey zone amyloid burden Table 3. Relationship between different amyloid positivity thresholds and longitudinal performance on a memory task Threshold Amyloid status Estimated annual change AIC Visual assessment Negative 0.19 (0.05) 2933.7 Positive -0.28 (0.09)** BPND 0.19 Negative 0.19 (0.05) 2938.5 Positive -0.22 (0.08)** 0.23 Negative 0.17 (0.05) 2935.8 Positive -0.28 (0.11)** 0.29 Negative 0.15 (0.05) 2938.2 Positive -0.28 (0.12)** SUVr 1.28 Negative 0.16 (0.05) 2941.2 Positive -0.21 (0.10)** 1.34 Negative 0.14 (0.05) 2940.0 Positive -0.28 (0.12)** 1.43 Negative 0.14 (0.05) 2943.0 Positive -0.29 (0.13)** Values given are Beta (SE), as estimated by Linear Mixed Models (predictor: amyloid status, outcome: score on RAVLT delayed recall). Numbers reflect annual change in raw score points. Models are adjusted for age, sex, education and scanner type. ** p-value < 0.01. P-value represents the significance of the difference between a positive amyloid status compared to a negative amyloid status. AIC = Akaike information criterion, SE = standard error, RAVLT = Rey auditory verbal learning task, BPND = Binding potential, SUVr = standardized uptake value ratio. Relationship between grey zone amyloid burden and memory slope Next, we categorised participants based on an increasing number of quantiles to evaluate whether the association between amyloid burden and memory slope is based on a gradual change in amyloid burden. For all models, a gradually lower annual memory performance is seen with increasing amyloid levels (all p for trend <0.05). Subgroups with the lowest amyloid burden (1st halve, 1st third, 1st quarter, 1st fifth and K-low) showed a practice effect, with an increase in memory performance 3
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