Dental health can affect your brain and is linked to dementia, Alzheimer’s

Poor oral hygiene increases the risk of a variety of health problems, including heart disease, diabetes, cancer, rheumatoid arthritis, and premature death. However, in addition to the mouth and body, the condition of our teeth and gums is also crucial to our health.

New evidence suggests that what happens in our mouths affects what happens in our brains, and may even affect our risk of dementia.

“People should really realize that oral health is very important,” said Anita Visser, a professor of geriatric dentistry at the University of Groningen in the Netherlands.

According to a 2022 World Health Organization report, severe periodontal disease (chronic inflammation and damage to the gums and bones that support teeth) affects about 19% of the world's population over the age of 15, or more than 1 billion people. More research is needed, but 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 whether and how the health of our mouths and minds come together, but they have identified two potential culprits that may explain how gum disease leads to Alzheimer's: bacteria and inflammation.

Linking teeth and mental health

One of the first studies to document the link between gum disease, tooth loss and Alzheimer's disease focused on a group of elderly nuns who were part of a larger study of aging. Researchers tracked 144 nuns and found that those with severely missing teeth had a 6.4 times higher risk of developing dementia than those with fewer missing teeth.

Other recent longitudinal studies have also found that higher rates of tooth loss are associated with cognitive decline. A small 2016 study of 60 people with mild to moderate dementia showed that periodontitis was associated with a six-fold decline in cognitive ability.

Another 2017 study of nearly 28,000 Taiwanese patients reported that living with chronic periodontal disease for 10 years or more increased the risk of Alzheimer's disease by 1.7 times. A 2022 meta-analysis of 47 longitudinal studies showed that tooth loss and poor oral health are associated with cognitive decline and dementia.

This study paints a new picture of the link between poor oral health and dementia, but there are a number of confounding factors that prevent researchers from drawing clear causal conclusions.

The higher incidence of dental problems in people with dementia may be a symptom of cognitive decline, rather than a cause. People with dementia have difficulty maintaining oral health and are at increased risk of developing gum disease, meaning the link between oral and cognitive health may run both ways.

Other known risk factors for dementia, such as smoking and lower education, are also associated with poorer oral health. Mario Dioguardi, a dental science researcher at the University of Foggia, said in an email that tooth loss can have secondary effects, affecting nutrition and overall health, which can affect cognition.

It's really complicated,” said Visser, who recently co-wrote a review on the relationship between oral health and Alzheimer's disease. “That's why we can't say, 'Oh, if you have periodontitis, you're going to get Alzheimer's.'” But we now know that if you have severe periodontitis, you're going to get Alzheimer's. The chance of mutism is even greater.

Oral bacteria may infect the brain

Bacteria that normally live in our mouths can also infect the brain and may contribute to the neurodegeneration seen in Alzheimer's disease, research has found.

A 2019 study published in Science Advances reported that, Porphyromonas gingivalis Bacteria are a key causative agent of gum disease and can be found in brain autopsies of Alzheimer's patients. Bacterial DNA has also been detected in the cerebrospinal fluid of people who may have Alzheimer's disease.

Toxic enzymes come from Porphyromonas gingivalis Bacteria have also been found in the brains of Alzheimer's patients and are associated with the amount of tau protein pathology, a hallmark of the disease.

Orally infecting mice with bacteria causes Porphyromonas gingivalis The accumulation of DNA in the brain as well as beta-amyloid cellular waste, a hallmark of Alzheimer's disease.

Researchers were able to inhibit bacteria enzyme in infected mice Porphyromonas gingivalis, reduces amyloid-beta production and neuroinflammation. (However, a recent clinical trial targeting these bacterial enzymes failed, and the U.S. Food and Drug Administration suspended future trials.)

“The mechanism by which periodontal bacteria enter the central nervous system remains unknown,” Dioguardi writes, but can reach the brain through the blood circulation or along peripheral nerves.

Oral inflammation affects the brain

If we don't brush our teeth for a few days, each tooth will develop a thin biofilm called plaque, which is filled with acid-producing bacteria.

“Your body doesn't like these bacteria,” Visser said. “They're on the edges of your teeth and on the edges of your gums.”

As plaque builds up, the gums become inflamed as our immune system attempts to fight off the infection. Gingivitis is the mildest form of periodontal disease but is still reversible. Brushing your teeth and removing plaque allows your gums to heal.

But if gingivitis isn't resolved, more serious gum disease or periodontitis may develop.

“The whole body is fighting this bacteria,” Visser said.The immune system is really stimulated and alert and works very hard to fight these germs.

This chronic inflammation creates a vicious cycle: Gum swelling increases, and the gap between the teeth and gums widens, allowing more bacteria to enter, which not only causes inflammation of the gums, but also of the underlying bone. If this continues, the body will reject the tooth, causing it to loosen and eventually fall out.

This chronic inflammation able Spills from the mouth to other parts of the body. Gum disease is associated with an increase in pro-inflammatory molecules in the blood, Dioguardi said.

Chronic inflammation in the body in turn leads to chronic neuroinflammation in the brain, which induces neurodegeneration and plays a key role in Alzheimer's disease.

Visser is conducting a longitudinal study collecting oral health data (dental X-rays and bacterial samples) from hundreds of patients with cognitive impairment to learn more about how oral health affects cognitive risk.

“We've seen some very serious cases of oral health problems that doctors are ignoring,” she said.

The challenge of untangling the relationship between our lifestyles, teeth and brains remains. “There are a lot of confounding factors, lifestyle, smoking, education, diet,” Visser said. “So it's really hard to do this research.”

Researchers stress that until more is known, oral hygiene remains one of the simplest and most important ways to take care of yourself.

Raising awareness of the increased risk of Alzheimer's disease associated with tooth loss and periodontitis can increase attention to oral health,DioGuardi said in an email.

For the sake of better health—and probably a healthier brain—keep brushing.

Do you have questions about human behavior or neuroscience?e-mail We may answer this question in a future column.

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