Worldwide, dementia affects 47 million people, 60-80% of those affected are diagnosed with dementia of the Alzheimer’s type. In a recent review published in June 2019 in the journal Periodontology 2000, the authors aimed to (1) assess the literature to evaluate the possibility of a causal relationship between periodontal disease and Alzheimer’s disease and dementia, and (2) to identify essential gaps in the literature requiring further exploration.1
The authors used Hill’s criteria when reviewing the literature for this review to determine causation. The authors hypothesize, “periodontal disease is causally related to dementia o the Alzheimer’s type.”
After reviewing the literature, the authors identified 14 longitudinal studies, 6 case-control studies, and 7 cross-sectional studies that fit the criteria to be included in the review. The longitudinal studies consisted of 7 prospective and 7 retrospective studies. The studies included were conducted in multiple countries including Taiwan, Japan, France, Sweden, South Korea and the United States.
In one of the retrospective studies with 27,963 people aged over 50 years of age with a ten-year history of periodontal disease, the authors found these individuals had an increased risk of developing Alzheimer’s disease. Choi et al also found the risk of dementia was higher in individuals with periodontal disease without environmental risks, such as smoking, alcohol, and lack of exercise, which suggested that periodontal disease alone can constitute a risk factor.
One of the studies that was considered a “landmark” study followed 597 men aged 28-70 for more than 30 years the authors found that periodontal disease was a risk factor for cognitive decline particularly in those over age 45. In combination, the 14 longitudinal studies provide moderate support for consistency, one of the Hill’s criteria. Additionally, these studies indicate that long-term exposure may be necessary for an association between periodontal disease and dementia.
Kamer et al also discussed the pathogenic mechanism described by the studies reviewed. The authors highlight that “Alzheimer’s disease is a continuum in which the first pathological change occurs decades before the onset of dementia.” They go on to provide detailed mechanisms by which periodontal disease can affect each stage of Alzheimer’s disease.
This review is great and very in-depth, though there is no way to do it justice in this short summary, we encourage you to read it for yourself to get all the information that was reviewed and critically appraised.
In conclusion, the authors state, “Based on pathological, mechanistic, clinical, animal, and “in vitro” studies we showed that periodontal disease could induce systemic inflammation, blood-brain barrier disruption, neuroinflammation, brain amyloid neurodegeneration, and cognitive impairment. As these are well-known pathogenic pathways of Alzheimer’s disease, we conclude that periodontal disease, through its inflammatory and bacterial burdens, could be a “biologically plausible risk factor” for Alzheimer’s disease.”
- Kamer AR, Craig RG, Niederman R, Fortea J, de Leon MJ. Periodontal disease as a possible cause for Alzheimer’s disease. Periodontol 2000. 2020 Jun;83(1):242-271. doi: 10.1111/prd.12327. PMID: 32385876.