Although past studies have suggested a link between oral health and dementia, this is the first to pinpoint a specific gum disease bacteria in the brain.
Researchers looked at donated brain samples of 10 people without dementia and 10 people with dementia. They found the bacteria Porphyromonas gingivalis in the brains of four of those with dementia.
Everyday activities like eating and tooth brushing, and some dental treatment, could allow the bacteria to enter the brain. "We are working on the theory that when the brain is repeatedly exposed to bacteria and/or debris from our gums, subsequent immune responses may lead to nerve cell death and possibly memory loss," says Sim Singhrao, PhD, a senior research fellow at the university.
This could mean that visits to the dentist could be vital for brain health, she says.
More Research Needed
For now, "it remains to be proven whether poor dental hygiene can lead to dementia in healthy people," says St John Crean, dean of the School of Medicine and Dentistry. "It is also likely that these bacteria could make the existing disease condition worse."
Reacting to the findings, Alison Cook, director of external affairs at the U.K.'s Alzheimer's Society, said: "There have been a number of studies looking at the link between dementia and inflammation caused by factors including poor dental health, but this is not yet fully understood. This small study suggests that we need more research into this important area."
Also reacting to the study, Simon Ridley, PhD, head of research at Alzheimer's Research U.K., said: "We don't know whether the presence of these bacteria in the brain contributes to the disease, and further research will be needed to investigate this. It is possible that reduced oral hygiene, and therefore P. gingivalis infection, could be a consequence of later-stage Alzheimer's, rather than a cause.
"Other studies have suggested that infections, including oral infections, could be linked to Alzheimer's, and there is ongoing research in this area."
He said it will be important for future studies to consider looking back at dental records, to match these with oral hygiene during a person's life.