The presence of nanoparticles (NPs) in olfactory bulb neurons and intraluminal erythrocytes from lungs, frontal lobe, and trigeminal ganglia capillaries, plus the presence of Aβ42 plaques in 100% of the apolipoprotein E allele 4, aged MMC 25.1 +/− 1.5y carriers, supported the key role of NPs and APOE4 in the development of Alzheimer’s disease. Here, APOE is linked to Alzheimer disease.