In human AD tissue, synaptic density and pairing were negatively correlated with 3B3 burden (Spearman’s correlation coefficients, −0.854 for synapsin density, −0.989 for PSD density, −0.959 for synapsin pairing, −0.975 for PSD pairing; p < 0.05), while co-localization of synaptic puncta with AβO was positively correlated with 3B3 burden (Spearman’s correlation coefficients, 0.824 for 3B3-positive synapsin puncta, 0.973 for 3B3-positive PSD puncta; p < 0.05). Here, ABO is linked to Alzheimer disease.