12/03/2026
Causes of Alzheimer’s
Scientists have found that bacteria linked to gum disease may also appear in the brains of people with Alzheimer’s.
Scientists are studying a possible connection between gum disease bacteria and Alzheimer’s disease. The idea is not that oral bacteria directly cause Alzheimer’s, but that certain harmful microbes common in periodontal disease may influence processes in the brain related to the disease.
In several studies using human brain tissue and animal models, researchers have detected Porphyromonas gingivalis — a key bacterium involved in gum disease — in the brains of people with Alzheimer’s. This bacterium produces toxic enzymes called gingipains, which can damage proteins and brain cells. These toxins may also trigger inflammation and changes linked to Alzheimer’s, including amyloid plaque buildup and tau protein abnormalities.
Scientists believe oral bacteria could reach the brain in two possible ways. They may enter the bloodstream through inflamed or bleeding gums, or travel along nerve pathways connecting the mouth and brain. Once in the brain, bacterial toxins and the immune response they trigger could contribute to chronic inflammation, which is considered an important factor in neurodegenerative diseases.
However, this research does not prove that oral bacteria cause Alzheimer’s disease. It simply highlights a growing area of research showing that oral health and brain health may be more connected than previously thought.
Maintaining healthy gums and treating gum disease is important not only for oral health but also for reducing systemic inflammation that may affect long-term health, including the brain.
Research Paper
DOI: 10.1126/sciadv.aau3333
