“People should really realize that oral health is really important,” he said. Anita VisserProfessor of Geriatric Dentistry at the University of Groningen in the Netherlands.
According to the World Health Organization in 2022, severe periodontal disease (chronic inflammation and damage to the gums and supporting bones of the teeth) will affect approximately 19 percent of people over the age of 15, or more than 1 billion people worldwide. I am. report. Although more research is needed, recent observational studies suggest that oral health may be a modifiable risk factor for Alzheimer’s disease, the most common type of dementia.
Scientists are still studying if and how our oral and mental health intersect, but there is evidence to explain how periodontal disease can lead to Alzheimer’s disease. We’ve identified two possible underlying causes: bacteria and inflammation.
Connecting teeth and mental health
One of the first studies to document the link between periodontal disease, tooth loss, and Alzheimer’s disease focused on a cohort of older nuns as part of a larger study on aging. .track researchers 144 of the nuns They found that those with severe tooth loss were up to 6.4 times more likely to develop dementia than those with fewer teeth.
Other more recent longitudinal studies have also found that higher incidences of tooth loss are associated with lower cognitive function. in one Small survey in 2016 In 60 patients with mild to moderate dementia, periodontitis was associated with a six-fold increase in cognitive decline.
Another 2017 study of approximately 28,000 Taiwanese patients reported that having chronic periodontal disease for more than 10 years was equivalent to a 1.7-fold increase in periodontal disease. Alzheimer’s disease risk.a 2022 meta-analysis Of the 47 longitudinal studies, we reported that tooth loss and poor oral health were associated with both cognitive decline and dementia.
Although this study paints a new picture of the link between poor oral health and dementia, there are a number of confounding factors that prevent researchers from drawing definitive conclusions about causation.
The high rate of dental problems in people with dementia may be a symptom, rather than a cause, of cognitive decline. People with dementia have difficulty maintaining oral health and are at higher risk of developing dementia. periodontal diseaseIn other words, the association between oral and cognitive health may be bidirectional.
other Known risk factors In the case of dementia, smoking and low educational attainment are also associated. poor oral hygiene. Losing teeth has secondary effects that affect nutrition and overall health, and can also impact cognitive function. Mario Dioguardisaid researchers in the Department of Dental Sciences at the University of Foggia in an email.
“It’s really complicated,” Visser said. recent reviews About the relationship between oral health and Alzheimer’s disease. “That’s why we can’t say, ‘If you have periodontitis, you’ll get Alzheimer’s.'” But we now know that if you have severe periodontitis, you’re more likely to develop Alzheimer’s disease. . ”
Bacteria in the mouth can infect the brain
Research has found that bacteria that normally reside in our mouths can also infect the brain and cause the neurodegeneration of Alzheimer’s disease.
a 2019 survey In a paper published in Science Advance, P. gingivalis Bacteria, a major pathogen in periodontal disease, may be found in brain autopsies of Alzheimer’s patients. Bacterial DNA has also been detected in the cerebrospinal fluid of people diagnosed with possible Alzheimer’s disease.
toxic enzymes from P. gingivalis Bacteria were also found in the brains of Alzheimer’s patients and correlated with the amount of tau protein that is a hallmark of the disease.
When mice are orally infected with this bacterium, P. gingivalis Brain accumulation of DNA and amyloid beta cell waste, a hallmark of Alzheimer’s disease.
Researchers succeeded in inhibiting bacterial growth enzyme from infected mice P. gingivalis, reduces amyloid-β production and neuroinflammation. (A Recent clinical trials However, targeting these bacterial enzymes has been unsuccessful, and the Food and Drug Administration put on hold About upcoming exams. )
“The mechanisms by which periodontal pathogens access the central nervous system are still unknown,” but they may reach the brain through the blood circulation or along peripheral nerves, study co-author Dioguardi wrote. There is. recent reviews The role that periodontal disease and oral bacteria play in Alzheimer’s disease.
Mouth inflammation can affect the brain
If you don’t brush your teeth for several days, a thin biofilm called plaque forms on each tooth, which is full of acid-producing bacteria.
“Your body doesn’t like these bacteria,” Visser says. “They’re on the edges of the teeth and on the edges of the gums.”
When plaque builds up, the gums become inflamed as our immune system tries to fight off the infection. Gingivitis, the mildest form of periodontal disease, is still reversible. Brushing to remove plaque buildup allows your gums to heal.
However, if gingivitis is not addressed, a more severe form of periodontal disease, or periodontitis, can occur.
“Your whole body is fighting this bacteria,” Visser says. “The immune system is highly stimulated, alert, and working hard against these germs. ”
This chronic inflammation becomes a vicious cycle, and as the gums become swollen, the gap between the teeth and gums widens, allowing more bacteria to enter and potentially inflaming not only the gums but also the underlying bone. If this continues, your body will reject the tooth, causing it to become loose and eventually lose the tooth.
This chronic inflammation can Spills from the mouth onto other parts of the body. Periodontal disease is associated with symptoms such as: Increased pro-inflammatory molecules In the blood, Dioguardi said.
To obtain detailed information about how oral health affects cognitive risk, Visser collected oral health data (such as dental X-rays and bacterial samples) from hundreds of cognitively impaired patients. ) is conducting a longitudinal study.
Already, she says, “we’ve seen some very serious cases of oral health problems that doctors miss.”
The challenge of unraveling the relationship between our lifestyle, teeth, and brain remains. “There are so many confounding factors, including lifestyle, smoking, education level, and diet,” Visser says. “That’s why it’s really difficult to do this research.”
Researchers emphasize that until more is known, oral hygiene remains one of the simplest and most important ways to care for yourself.
“Raising public awareness about the increased risk of Alzheimer’s disease associated with tooth loss and periodontitis may lead to increased interest in oral health.” Dioguardi I said in an email.
For better health and perhaps a healthier brain, keep brushing your teeth.
Have questions about human behavior or neuroscience? Email BrainMatters@washpost.com I may answer that in a future column.
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