Number of APOE4 alleles positively correlated with amount of [11C]-PiB burden in precuneus of HCs, PD-MCI, PDD, and DLB groupsHaving at least one APOE4 allele was associated with higher precuneus [11C]-PiB retention by 2-fold when adjusting for diagnostic group and agePrecuneus [11C]-PiB uptake was not significantly related to MMSE scores for any of the PD-NC, PD-MCI, PDD, or HCs groups. Here, APOE is linked to Parkinson disease.