Dental Health and Dementia: Exploring the Link Between Oral Health and Cognitive Decline

Dental Health and Dementia: Exploring the Link Between Oral Health and Cognitive Decline about undefined

A trip to the dentist is not something any of us look forward to, but it’s important not to put it off. That’s because a regular dental check-up - as well as good oral health and oral hygiene at home - is a key strategy to prevent cognitive decline, dementia, and Alzheimer’s disease.

Research has been building on the link between oral health and cognitive impairment for some time. In fact, we've reported on the link between gum disease and dementia before. Now a new study starkly demonstrates how poor oral health and gum disease can shrink and age the brain, damaging memory.

Key Takeaways

  • Lab research and human studies demonstrate poor oral health and cognitive decline are connected.
  • Early intervention is key to preventing any potential impact on brain health.
  • Tooth loss and cognitive function are also linked. Good oral hygiene and the help of dental professionals can help prevent or delay tooth loss and future risk through regular visits and preventative measures.

The Oral Microbiome

The mouth is home to around 700 species of bacteria. In an oral cavity with gum disease - also called periodontal disease or periodontitis - the tight seal between the gums and teeth is weakened. This allows harmful bacteria, especially one called Porphyromonas gingivalis, to enter the bloodstream and reach the brain and other areas of the body. As we've reported before this can set off systemic inflammation that can contribute to physical decline and cognitive decline.

If gum disease were rare this wouldn’t be of much concern, but it's actually one of the world’s most prevalent diseases. In the U.S. gum disease affects 47.2 percent of adults aged 30 and older. But older adults and elderly patients have even more to worry about because an alarming 70.1 percent of seniors are affected by periodontal disease according to the CDC.

If periodontal disease is a potential cause of cognitive decline, then maintaining good oral health could be one of the most important health practices we can adopt. This makes it crucial for each of us to assess periodontal health.

Tooth Loss, Dental Health and Dementia

Among 2,355 participants aged 60 or more, those with the most gum disease had the worst verbal memories and the least ability to perform mathematical calculations.

A meta analysis of five high quality studies concluded that gum disease is linked to Alzheimer’s and if periodontitis is severe, it triples the likelihood of Alzheimer’s disease. This is not the first time we've reported this link between gum disease and a dramatic increase in Alzheimer's disease.

Another research review that included 47 studies found that poor periodontal health was linked to a 21 percent increased risk of dementia or mild cognitive impairment (MCI) and a 23 percent greater likelihood of developing cognitive decline. Tooth loss, independent of gum disease, was also linked to cognitive decline.

Impairs Ability to Chew

Tooth decay leading to tooth loss impairs the ability to chew. Good chewing ability is important because it stimulates blood flow to the brain and activates different areas of the brain. The risk of cognitive impairment and cognitive decline increases with each lost tooth, so even partial tooth loss is of concern.

In a meta analysis involving 34,074 adults, those with more tooth loss had a 48 percent higher risk of developing cognitive impairment and a 28 percent higher risk of receiving a dementia diagnosis. Lead study author Xiang Qi explained, saying, “This ‘dose-response’ relationship between the number of missing teeth and risk of diminished cognitive function substantially strengthens the evidence linking tooth loss to cognitive impairment, and provides some evidence that tooth loss may actually predict cognitive decline.”

The latest human study was led by Satoshi Yamaguchi, PhD, DDS, of Tohoku University in Sendai, Japan. Its findings on cognitive function are concerning.

Gum Disease Shrinks The Brain

The study included 172 cognitively health men and women aged 55 and over. When the study began, they had brain scans, dental examinations to assess their periodontal health, and memory tests. This was repeated four years later.

The team found the amount of gum disease and the number of teeth lost was linked to changes in the left hippocampus, a key learning and memory area of the brain.

Those with mild gum disease and fewer teeth had a faster rate of brain shrinkage in the left hippocampus. Is this a big deal? You bet. Think of it this way: The increase in the rate of brain shrinkage due to one less tooth was equivalent to nearly one entire year of brain aging.

We've written before about the dangers of brain shrinkage and what you can do about it.

More Teeth Can Also Be Bad News

Interestingly, for those with severe gum disease, having more teeth was linked to a faster rate of brain shrinkage. Having one more tooth was equivalent to 1.3 years of brain aging. This is because with severe disease each tooth is badly infected, so the more teeth a person retains the worse their oral health and the greater their chance of cognitive decline.

Commenting on the findings, Dr. Yamaguchi said: “Tooth loss and gum disease…are very common, so evaluating a potential link with dementia is incredibly important. Our study found that these conditions may play a role in the health of the brain area that controls thinking and memory, giving people another reason to take better care of their teeth. These results highlight the importance of preserving the health of the teeth and not just retaining the teeth. Controlling the progression of gum disease through regular dental visits is crucial.”

All the above human studies clearly demonstrate that periodontal health and cognitive impairment are linked but they cannot prove directly that gum disease causes cognitive decline and is one of the main risk factors. To find out if this could be the case, scientists put on their white coats and returned to the lab.

Gingipains: Evidence For a Direct, Causal Connection

A team of international scientists discovered that poor oral health leading to infection with P. Gingivalis led to the production and colonization of amyloid beta in the brains of mice. While this protein is considered a hallmark of Alzheimer’s, animal studies show it also has a direct role in clearing infections from the brain.

P. Gingivalis also secretes neurotoxic enzymes called gingipains. These were found in the brain cells of deceased Alzheimer’s patients. Gingipains damage tau, a protein that’s necessary for normal brain cell function and is hallmark of Alzheimer's disease.

Senior author Jan Potempa explained, saying that “we now have strong evidence connecting P. gingivalis and Alzheimer’s pathogenesis…”

Their work demonstrates that both hallmarks of Alzheimer's disease may occur as a response to an infection stemming from adverse oral health. And this could, according to the scientists, play a central role in the origin and development of cognitive decline and Alzheimer's disease.

Risk Factors: Oral Bacteria Promote Neuroinflammation

Their findings on the impact of oral health on cognitive function were backed up in new research by scientists at the Forsyth Institute, Cambridge, MA, and Boston University. Their analysis revealed that gum disease causes a change in the brain’s microglial cells. These immune cells are responsible for protecting the brain from amyloid beta plaques. In mice, oral bacteria crossed the blood brain barrier and chronically overstimulated the microglia. This promoted neuroinflammation and prevented the microglia from digesting the plaques.

Senior author Alpdogan Kantarci said: “This study suggests that in order to prevent neuroinflammation and neurodegeneration, it will be critical to control the oral inflammation associated with periodontal disease. The mouth is part of the body and if you don’t take care of oral inflammation and infection, you cannot really prevent systemic diseases, like Alzheimer’s.”

We've written before about the dangers of neuroinflammation and how it can cause amyloid beta plaques and tau proteins to grow.

What You Can Do To Protect Yourself

With human studies showing a clear link between poor oral health, tooth loss and poor cognitive function, we must pay close attention to the health of our gums and teeth.

The Importance of Regular Dental Check-Up's

As part of your daily routine, note any changes such as redness, swelling, receding gums, pain when chewing, or teeth that aren’t firmly fixed in place. Even without these signs, periodontal disease could still be present. That’s where the dentist comes in.

The dental exam will include the use of a periodontal probe which is inserted between each tooth and surrounding gum. If the probe drops below the healthy range of one to three millimeters, it indicates gum inflammation. Any bleeding that occurs during probing also indicates inflammation.

Dental x-rays will also be carried out, at least on the first visit and then as necessary depending on the state of your oral health. These are necessary because there’s no other way of assessing the condition of the roots, jaw, and facial bone composition. Improvements in technology mean patients are only exposed to minimal amounts of radiation. However, if you have concerns about x-rays as many natural doctors do, discuss with your dentist about how to proceed.

When choosing a dentist, one who practices functional, biologic or holistic dentistry is preferable because they take a whole-body approach to oral health that looks at the root cause of problems, and common risk factors, emphasizing the importance of the oral microbiome. They will be fully aware of the connection between periodontal and cognitive health.

Dental Care at Home

The growth of microorganisms develops within a few days if oral health measures are skipped, so teeth brushing needs to be a daily practice. Brush teeth at least two minutes twice a day and use dental floss at least once a day. For those who find floss hard to use, a vibrating flosser called the Slate Electric Flosser was introduced last year. Water based electronic flossers are also available, but they can miss key problem areas.

Eat a healthy, wholefood diet with plenty of fruits and vegetables. This not only provides the nutrients needed for healthy gums and teeth, as well as supporting the oral microbiome, but also provides varied textures that require chewing. A good diet also promotes healthy saliva production which is vital for good oral health.

Saliva has multiple functions. It promotes good digestion, maintains a healthy oral microbiome, delivers minerals to the teeth, and helps prevent cavities and mouth sores. Some medications limit saliva production and dry the mouth but a more common cause of dry mouth is mouth breathing, especially at night.

Functional dentistry expert Mark Burhenne, DDS, considers “mouth breathing the number one cause of cavities—even ahead of poor diet or bad dental hygiene.” He recommends using a special mouth tape called SomniFix at bedtime or even during the day to help train the body to nose breathe.

He also advises against conventional mouthwashes because they also dry the mouth as well as disrupt the oral microbiome. Mouthwashes can actually worsen oral health. Mouthwashes aren’t necessary, he believes, but if you want to use one, find an all-natural variety.


In conclusion, there's a clear connection between poor dental health, tooth loss, and cognitive decline. You can take action now by adopting good general health and oral hygiene practices and having regular dental check-ups. By doing so you'll not only preserve your periodontal health but you can protect your memory and help prevent cognitive decline and dementia.

Frequently Asked Questions

  • What is the link between dementia and dental health?

    Existing evidence links poor oral hygiene to dental cavities or caries. Poor oral hygiene and tooth loss disrupts the oral microbiome, potentially causing harmful bacteria to enter the bloodstream and find their way to the brain. This may trigger neuroinflammation and brain cell damage that puts you at significantly higher risk of mild cognitive impairment, dementia, and other neurodegenerative diseases.

  • Can unhealthy gums increase your odds of dementia?

    Many lab and human studies show periodontitis is linked to an increased risk of cognitive decline, poor cognitive function, and dementia. Tooth loss, infected gums, and bone loss in the jaw are all associated with a higher risk.

  • Is it really necessary to seek the services of a dentist?

    Nobody likes to visit a dental office, but dental professionals play an important role in helping adults of all ages, including older adults, to maintain healthy oral tissues, improve oral health, and prevent tooth loss. They can check your oral status, pick up problems at an early stage and treat them before they develop into a serious problem. By doing so they can help you maintain cognitive performance, minimize the risk of cognitive decline and prevent dementia onset.

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