In 2019 a paper published in the journal Science Advances sent ripples through both the dental and neuroscience communities. Researchers found evidence of Porphyromonas gingivalis and its toxic enzymes called gingipains in the brains of Alzheimer’s disease patients at significantly higher levels than in control brains. A pharmaceutical company subsequently began clinical trials of gingipain inhibitors as potential Alzheimer’s treatments. This is an extraordinary development if even partially borne out.
What the 2019 study found
The Dominy et al. study examined post-mortem brain tissue from people who had died with Alzheimer’s disease and from controls without cognitive decline. They found gingipain enzymes in 91 to 96 percent of Alzheimer’s brain samples, P. gingivalis DNA in multiple brain regions, and in mouse models P. gingivalis oral infection resulted in bacterial colonization in the brain and amyloid beta production. In the mouse models gingipain inhibitors reduced bacterial load, reduced amyloid beta, and reduced neuroinflammation.
The supporting epidemiological evidence
Multiple large longitudinal studies have found associations between periodontal disease or tooth loss and cognitive decline or dementia. A 2020 meta-analysis of 47 studies found significant associations between poor oral health and cognitive decline. A large Danish study found that people with periodontitis had a significantly higher risk of developing Alzheimer’s over a decade of follow-up. These associations are consistent across populations and methodologies.
The gingipain inhibitor trials
Cortexyme the company that filed patents on gingipain inhibitors for Alzheimer’s treatment ran clinical trials. The results as of 2026 have been mixed with initial data showing some signal but concerning safety findings and the program has faced setbacks. The hypothesis is still being tested by other researchers. This does not invalidate the underlying biology but means the direct therapeutic application remains unproven.
What this means practically
The honest interpretation: the evidence is genuinely interesting and mechanistically plausible. The association between poor oral health and cognitive decline is real and consistent. Whether it is causal and whether treating gum disease reduces Alzheimer’s risk has not yet been definitively established. What is clear is that periodontal disease is worth treating for its own sake. For comprehensive gum health support see our dental supplement guide and our guide to periodontal disease.
Educational content. Do not interpret this article as claiming that treating gum disease prevents dementia. The research is ongoing.
