Your teeth and your brain are both housed in your head, but what does oral care have to do with the health of your brain? That’s the question scientists were trying to answer when they discovered that periodontal disease—an inflammatory condition that eventually leads to the loss of teeth—could kickstart Alzheimer’s disease.
Researchers at the University of Illinois in Chicago conducted a study published in the journal PLOS One that showed mice with the bacteria that causes gum disease had inflammation and deterioration in their brains, too.
“Other studies have demonstrated a close association between periodontitis and cognitive impairment, but this is the first study to show that exposure to the periodontal bacteria results in the formation of senile plaques that accelerate the development of neuropathology found in Alzheimer’s patients,” said Dr. Keiko Watanabe, professor of periodontics at the UIC College of Dentistry and corresponding author on the study.
Watanabe is referring to previous studies that have shown that people who have gum disease for ten or more years have a higher risk of dementia by up to 70 percent. Those studies analyzed over 28,000 people and concluded that those who brush their teeth more are less likely to develop the disease.
For this study, Watanabe and his colleague applied the periodontal bacteria to the mouths of 10 mice for 22 weeks. They then compared the brain tissue of those mice to a control group. The mice exposed to the bacteria had more inflammation and fewer neurons still intact in their brains. Through an analysis of the proteins in the tissue, they saw that the exposed mice had more beta-amyloid plaques—a biomarker of Alzheimer’s disease.
“Our data not only demonstrate the movement of bacteria from the mouth to the brain, but also that chronic infection leads to neural effects similar to Alzheimer’s,” Watanabe said.
When scientists looked at the RNA in the brain, they saw that more genes associated with inflammation were expressed in mice with the bacteria. Inflammation has been pinpointed as a potential cause of Alzheimer’s and the formation of plaques.
“This was a big surprise,” Watanabe said. “We did not expect that the periodontal pathogen would have this much influence on the brain, or that the effects would so thoroughly resemble Alzheimer’s disease.”
Dementia isn’t the only disease associated with Alzheimer’s; oral health has been tied to cancers like HPV as well as cardiovascular disease. Some studies have shown that the bacteria that breaks down gums and loosens teeth can transfer into the bloodstream, raising the protein that triggers inflammation.
“Oral hygiene is an important predictor of disease, including diseases that happen outside the mouth,” she said. “People can do so much for their personal health by taking oral health seriously.”