Evidence and Therapeutic Perspectives in the Relationship between the Oral Microbiome and Alzheimer’s Disease: A Systematic Review

Abstract

This review aims to clarify the nature of the link between Alzheimer’s disease and the oral microbiome on an epidemiological and pathophysiological level, as well as to highlight new therapeutic perspectives that contribute to the management of this disease. We performed a systematic review, following the Preferred Reporting Items for Systematic Reviews checklist, from January 2000 to July 2021. The terms “plaque,” “saliva,” and “mouth” were associated with the search term “oral diseases” and used in combination with the Boolean operator “AND”/”OR”. We included experimental or clinical studies and excluded conferences, abstracts, reviews, and editorials. A total of 27 articles were selected. Evidence for the impact of the oral microbiome on the pathophysiological and immunoinflammatory mechanisms of Alzheimer’s disease is accumulating. The impact of the oral microbiome on the development of AD opens the door to complementary therapies such as phototherapy and/or the use of prebiotic compounds and probiotic strains for global or targeted modulation of the oral microbiome in order to have a favourable influence on the evolution of this pathology in the future.

Associations between self‐reported periodontal disease and nutrient intakes and nutrient‐based dietary patterns in the UK Biobank

“…It is a major cause of tooth loss, which consequently can lead to poor nutritional status, low self‐esteem, and reduced quality of life (Tonetti et al, 2017). A growing body of evidence also suggests that periodontal disease is associated with several conditions, including diabetes, cardiovascular diseases, cancer, rheumatoid arthritis, pre‐eclampsia, dementia, and Alzheimer's disease (Chapple et al, 2013; Tonetti et al, 2013; Bourgeois et al, 2019; Nadim et al, 2020; Bora et al, 2021; Gare et al, 2021; Maitre et al, 2021). Periodontal diseases are among the most prevalent chronic infections in humans.…”

Oral-Hygiene-Related Mobile Apps in the French App Stores: Assessment of Functionality and Quality

“…In Europe, oral diseases represent the third highest health care expenditure compared to other noncommunicable diseases [ 5 ]. In addition, oral diseases are risk factors for noncommunicable diseases such as cardiovascular diseases, diabetes, cancer, Alzheimer’s, and adverse pregnancy outcomes [ 6 , 7 , 8 , 9 , 10 ].…”

Oral Microbiota, Its Equilibrium and Implications in the Pathophysiology of Human Diseases: A Systematic Review

“…The pathogens that cause periodontitis are mainly anaerobic Gram-negative bacteria [ 17 , 59 ]. The high immune response that the presence of these bacteria causes withing the oral gums leads to high production of pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), as a response from the host immune system [ 60 , 61 ]. Periodontitis is also associated with increased serum levels of C-reactive protein (CRP) and decreased anti-inflammatory markers such as interleukin-10 [ 61 ].…”

“…The high immune response that the presence of these bacteria causes withing the oral gums leads to high production of pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), as a response from the host immune system [ 60 , 61 ]. Periodontitis is also associated with increased serum levels of C-reactive protein (CRP) and decreased anti-inflammatory markers such as interleukin-10 [ 61 ]. This results in a first stage of severe gingival inflammation, followed by an irreversible loss of the tooth supporting tissues (the periodontal ligament and alveolar bone) [ 62 , 63 ].…”