The MMSE score, MoCA score, serum miR-27a-3p level, cerebrospinal fluid miR-27a-3p, Aβ42 levels and Aβ42/Aβ40 ratio of AD patients in mild group and moderate-to-severe group were all lower than those in the control group, and the moderate-to-severe group were lower than the mild group (all P < 0.05);the serum NEAT1 level, SUVR, and cerebrospinal fluid NEAT1 and BACE1 levels were higher than those in the control group, and the moderate-to-severe group were higher than the mild group (all P < 0.05). This evidence concerns the gene BACE1 and Alzheimer disease.