APOE and dementia: In general, our SCD Aβ− individuals were the youngest, our MCI Aβ− and DLB groups had less females, APOE ε4 carriage was most common in the Aβ+ groups (SCD, MCI, AD‐dementia, but also in DLB), and MMSE was highest in the SCD groups followed by the MCI groups, and was lowest in the dementia groups (AD‐dementia, FTD, DLB) (p‐values for all demographic group comparisons are presented in Table S2).