137 Cerebral blood flow, amyloid burden and cognition RESULTS Demographics Table 1 shows the baseline demographics of the sample. One-hundred-and-eightyseven individuals were on average 64.6±7.6 years old, 74 (39%) were female, MMSE was 28.9±1.2 and 69 (39%) were APOE ε4 carrier. Fazekas score and number of microbleeds were low. Eighty-three individuals underwent follow-up PET. Individuals in this subset were similar to the total sample in terms of baseline demographics. In this cognitively normal group, we found on average only very subtle changes over time. BPND increased over time in frontal, temporal, parietal and composite regions, with the greatest change in the frontal region (beta 0.02 (SE 0.003)). On average, R1 also increased over time in frontal and temporal regions (0.01 (0.002); 0.00 (0.001)), but decreased subtly in the parietal region (-0.00 (0.002)). Baseline neuropsychological test scores were within age- and education-dependent norms. Over time and for the whole sample, we found a small improvement on RAVLT immediate, RAVLT delayed, Stroop II and Stroop III, while the score on VAT-A became somewhat lower over time. Table 1. Baseline demographics Total N=187 Demographics Age, mean±SD 64.61±7.61 Sex, n female (%) 73 (39.04%) Education, median[IQR] 6 [5-6] APOE ε4 carriership, n (%) 69 (39.20%) Amyloid positivity, n (%)† 45 (24.06%) Fazekas, mean±SD 0.88±0.79 Microbleeds, n (%)‡ 32 (17.11%) Concurrent Annual change Amyloid burden BPND Frontal 0.18 (0.012) 0.02 (0.003)* BPND Temporal 0.13 (0.009) 0.01 (0.002)* BPND Parietal 0.21 (0.012) 0.01 (0.002)* 6