APOE4, Alzheimer's and periodontal disease: A scoping review

The ε4 allele of the apolipoprotein E gene (APOE4) is recognized as the primary genetic risk factor for Alzheimer's disease (AD) and has been associated with chronic inflammatory conditions, such as periodontal disease (PD). PD has been identified as having a potentiating effect that favors the development and progression of AD. This scoping review investigates the potential relationship between PD and AD through APOE4.

The Joanna Briggs Institute methodology and PRISMA guidelines were followed. The search included articles published in PubMed and Embase, focusing on human studies, and excluding case series, in vitro studies, reviews, and animal studies.

Among the studies that evaluated the relationship between PD, APOE4, and AD, a correlation was identified between the gingival index and cognitive impairment in APOΕ4 carriers. Additionally, higher levels of apolipoprotein E4 were found in the crevicular fluid of patients with both AD and PD, compared to individuals without AD.

APOE4 may link PD and AD through shared genetic variants, inflammatory pathways, and dyslipidemia, involving both peripheral and central pathways. More comprehensive studies are required to ascertain the relationship between PD, AD, and APOE4, and to determine whether these associations are causal or non-causal in nature.