A new study from the United Kingdom found gum disease in the autopsies of individuals who died with Alzheimer's disease and its absence in a similar group who did not have dementia. That raises the question, the researchers say, of whether dental hygiene could head off the neurodegenerative disease.
The study, by a team at the University of Central Lancashire (UCLan), looked at 10 brain samples from patients with the dementing condition and found in each case evidence of Porphyromonas gingivalis, which leads to unhealthy gums.
The findings were published in the Journal of Alzheimer's Disease.
In background material, the researchers explained that "these bacteria enter the bloodstream through daily activities, such as eating, chewing and tooth brushing, but especially following invasive dental treatment, and from there, potentially enter the brain on a regular basis. The researchers propose that every time they reach the brain, the bacteria may trigger immune system responses by already primed brains cells, causing them to release more chemicals that kill neurons. This could be one mechanism that leads to changes in the brain, which is typical of Alzheimer’s disease, and could be responsible for causing symptoms such as confusion and deteriorating memory.
According to an article in the Express, "Researchers believe that when the bacteria reach the brain in the bloodstream, they trigger an immune response that can lead to the death of brain cells called neurons. This process could help drive the changes that are typical of Alzheimer's disease, causing symptoms of confusion and brain loss."
The findings, by the researchers' own admission, is interesting but not definitive. The Alzheimer's Society in England issued a statement telling people to keep it in perspective. Wrote Dr. Alison Cook, director of external affairs, "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.
"The best way to reduce your risk of dementia is to lead a healthy lifestyle. Enjoy a balanced Mediterranean diet," Cook said, that includes plenty of vegetables and fruits, and oily fish, as well as getting regular exercise and not smoking. "Of course, if people are worried, it never hurts to reach for the toothbrush twice a day."
An article in Medical Daily was more skeptical. Jonathan Weiss wrote, "The research in no way proves or even shows that the specific bacterial species causes Alzheimer's disease. It just shows that the bacteria have a higher chance of making it into the brain of affected individuals. This is easily understandable because the beta-amyloid plaques found in the brains of Alzheimer's patients cause inflammation. This inflammation can cause the impermeable blood brain barrier to become porous and hearty bacteria, such as those that cause gingivitis, can make their way into the brain.
"This brings to mind the story years back about similar oral bacteria being implicated in heart disease. Researchers found that several species that can cause gum disease were found in plaques of atherosclerosis found in patients with heart disease. The myth that oral hygiene can lead to heart attacks was finally dispelled in a 2012 paper published in the American Heart Association's journal Circulation."
Still, UCLan researchers said it adds another piece to the puzzle that is Alzheimer's, which afflicts as many as 5 million Americans, according to the National Institute on Aging. Because the incidence increases with age, that number is expected to grow rapidly as baby boomers reach old age.
"This new research indicates a possible association between gum disease and individuals who may be susceptible to developing Alzheimer's disease, if exposed to the appropriate trigger," said StJohn Crean, dean of the School of Medicine and Dentistry at UCLan. "But it remains to be proven whether poor dental hygiene can lead to dementia in healthy people, which obviously could have significant implication for the population as a whole. It is also likely that these bacteria could make the existing disease condition worse."
UCLan said the findings are bolstered by not-yet-published research from the same scientists in collaboration with the University of Florida, where they used animal models to show that P. gingivalis in the mouth finds its way to the brain once the periodontal disease becomes established.
“We are working on the theory that when the brain is repeatedly exposed to bacteria and/or their debris from our gums, subsequent immune responses may lead to nerve cell death and possibly memory loss. Thus, continued visits to dental hygiene professionals throughout one’s life may be more important than currently envisaged with inferences for health outside of the mouth only. To help us prove our hypothesis, we are hoping to use the Brains for Dementia Research tissue resource to examine brain tissue from people with both intact and compromised memory who have relevant dental records. The future of the research aims to discover if P. gingivalis can be used as a marker, via a simple blood test, to predict the development of Alzheimer disease in at-risk patients,” Dr. Sim K. Singhrao, senior research fellow at UCLan, said in a written statement the accompanied the journal article.
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