Gingipain K (K-GP) level was significantly correlated with Aβ, phosphorylated tau 199 and synaptosomal-associated protein 25 levels in the cerebrospinal fluid from AD-D with periodontitis group (all <i>p</i> < 0.05).<h4>Conclusion</h4>Periodontitis is more prevalent and severe in AD patients. This evidence concerns the gene MAPT and periodontitis.