Oral health and brain health: is there a connection? The answer to this question is steadily revealing itself as part of medical research. Today, scientists are discovering that chronic inflammation and harmful oral bacteria could shape the development and progression of cognitive decline.
For those of you caring for a parent with memory loss, noticing changes in your own gums, or you simply want to take better care of your health, this article explores what the research shows, what’s not been proven yet, and offers you practical steps toward better overall health.
The Growing Impact of Alzheimer’s Disease
Alzheimer’s disease affects millions of families every year.
- Around one in nine adults aged 65 and older (about 11%) has Alzheimer’s disease, according to the Alzheimer’s Association 2026 Facts and Figures report. That’s an estimated 7.4 million Americans.
- It is one of the leading causes of death in the US. In 2024, it was officially listed as the fifth-leading cause of death among people aged 65 and older.
- Changes within the brain, including the accumulation of amyloid plaques and tau proteins, may begin 10 to 20 years before any symptoms appear. The National Institute on Aging notes that damage to the brain possibly starts a decade or earlier before memory problems become noticeable.
It’s worth noting that because changes in the brain develop long before memory loss becomes visible, the focus on reducing chronic inflammation throughout the body has become an important area of research.
In simple terms, the period before an Alzheimer’s diagnosis has become much more important because it means that the daily habits you build in your 40s, 50s, and 60s, including how you care for your gums, are part of your bigger picture in terms of healthy aging.
The Oral-Systemic Connection
Periodontal (gum) disease is a chronic inflammatory infection that’s caused by harmful bacteria under the gumline. Researchers have discovered that people with this disease tend to have a higher risk of cognitive decline and Alzheimer’s disease.
The causality of this relationship is still being studied. However, chronic oral inflammation is believed to contribute to systemic inflammation that may affect the brain.
What the long-term studies show
One of the most cited international studies followed patients in Taiwan’s national health insurance database for over a decade. Researchers found that people who had lived with chronic periodontitis for 10 years or more were about 1.7 times more likely to develop Alzheimer’s disease than people without gum disease, even after accounting for conditions such as diabetes, heart disease and stroke (Chen et al., Alzheimer’s Research & Therapy, 2017).
Interestingly, this study found no clear link for shorter periods of gum disease, which suggests that how long inflammation goes untreated could be a decisive factor.
Another study looked at blood samples taken from older adults years before any memory problems began. People who later developed Alzheimer’s had higher antibody levels to certain gum disease bacteria. This is a sign that their immune system had been fighting these germs long before their diagnosis (Sparks Stein et al., Alzheimer’s & Dementia, 2012).
Why inflammation is the common theme
Healthy gums act like a protective barrier. But when gum disease breaks that barrier, bacteria and the inflammatory signals your body produces to fight them can enter the bloodstream daily.
Over time and several years, this low-grade, body-wide inflammation is one of the routes researchers believe may connect the mouth to the brain.
The good news is that gum inflammation is something you can see, measure, and treat. Today, treatment options even include laser gum disease therapy.
Tooth Loss and Risk of Dementia
Several studies have also shown that individuals with fewer remaining natural teeth have a higher risk of developing dementia, which highlights the importance of preserving healthy teeth as far as possible.
A 2021 analysis by researchers at New York University combined 14 long-term studies with more than 34,000 participants (Qi et al., JAMDA, 2021). They reached the following conclusions:
- People with higher tooth loss were at greater risk of cognitive impairment and dementia.
- The risk rose steadily with each additional tooth lost, which is a “dose-response” pattern that strengthens the case for a significant connection.
- Among people who had replaced missing teeth with dentures, the link was no longer statistically significant (NYU summary).
The researchers point to several possibilities for these findings.
Firstly, gum disease is a leading cause of tooth loss, and missing teeth can make it harder to chew and eat a nutritious diet. As such, tooth loss can reflect a lifetime of limited access to care.
This is a big part of our philosophy at Forever Smiles: we focus on saving teeth first and doing implants only when necessary.
If you’ve been told your teeth need to come out, a comprehensive second opinion can help you understand your options before deciding. When a tooth can’t be saved, replacing it promptly with dental implants or implant-supported dentures helps you keep chewing comfortably and eating well.
Oral Bacteria and Alzheimer’s Disease
Researchers have identified several periodontal bacteria that may be associated with Alzheimer’s disease, including:
- Treponema denticola (TD)
- Tannerella forsythia (TF)
- Porphyromonas gingivalis (Pg)
- Aggregatibacter actinomycetemcomitans (AA)
In a study of older adults in northern Manhattan, researchers measured blood antibodies to these same gum disease bacteria and followed participants for approximately five years. Antibody levels to common periodontal bacteria were associated with the risk of developing Alzheimer’s (Noble et al., PLoS ONE, 2014).
Your saliva carries clues about which bacteria live in your mouth. Learn more about this in our post on What’s Lurking in Your Saliva?
Porphyromonas gingivalis: the most studied culprit
One organism receiving significant scientific attention is Porphyromonas gingivalis, which is a major cause of periodontal disease. Lab studies indicate that this bacterium and its inflammatory toxins could contribute to chronic inflammation in the brain.
In 2019, an international research team found P. gingivalis and its toxic enzymes, called gingipains, in the brain tissue of people who had passed away with Alzheimer’s. Gingipain levels were tracked with tau, also known as one of the proteins that builds up in Alzheimer’s. In mice, an oral P. gingivalis infection spread to the brain and increased production of amyloid beta, which is the protein that forms plaques (Dominy et al., Science Advances, 2019).
Oral spirochetes in the brain
Studies have also detected oral spirochetes in the brains of many individuals with Alzheimer’s disease. This suggests that oral bacteria may play a role in the disease process. Researchers continue to investigate exactly how these bacteria may contribute to cognitive decline.
In one early study, oral Treponema (a type of spirochete) were found in the brain tissue of 14 out of 16 people with Alzheimer’s, compared with four out of 18 people without it (Riviere et al., Oral Microbiology and Immunology, 2002).
While the study was small, it helped launch two decades of research into how oral bacteria might reach the brain.
Alzheimer’s Disease and “Type 3 Diabetes”
Some researchers have referred to Alzheimer’s disease as “Type 3 diabetes” because of evidence that insulin signaling and glucose metabolism may become impaired within the brain.
The term was popularized by Dr. Suzanne de la Monte of Brown University. Her research review described insulin resistance and insulin deficiency in the brain as features of Alzheimer’s (de la Monte & Wands, Journal of Diabetes Science and Technology, 2008).
Although this term is not an official medical diagnosis, it emphasizes the rising understanding that metabolic health, chronic inflammation, and brain function are closely intertwined.
Diabetes and gum disease are closely linked as high blood sugar makes gum infections harder to control. And gum inflammation can make blood sugar harder to manage. Hence, caring for your gums is one more way to support your overall metabolic health.
What the Research Doesn’t Show (Yet)
We believe you deserve honest, factual information instead of fear tactics and hype. So, here is a brief overview of where the science currently stands:
- Association is not proof of cause: Gum disease is associated with a higher risk of cognitive decline, but studies have not proven that gum disease causes Alzheimer’s.
- The link may run both ways: As memory declines, brushing and flossing often become harder, which can worsen gum health. Researchers are still determining which one comes first.
- Treatments aimed at gum bacteria are still experimental: A large clinical trial tested a drug designed to block P. gingivalis toxins in people with mild to moderate Alzheimer’s. It did not meet its main goals in the overall group of 643 participants (GAIN Trial results, 2021) and research continues.
What the evidence does support is that healthy gums mean less chronic inflammation in your body. Also, keeping your natural teeth helps you eat well and live well.
Simple Steps to Protect Your Gums and Your Overall Health
You don’t need to overhaul your life. Small, steady habits make the biggest difference:
- Brush twice a day with a soft-bristle brush, angling the bristles toward the gumline.
- Clean between your teeth every day with floss, interdental brushes, or a water flosser to help prevent gum disease.
- Watch out for warning signs, including gums that bleed when you brush, redness or swelling, persistent bad breath, gums pulling back, or teeth that feel loose.
- Keep up with professional cleanings and comprehensive exams so problems are caught early.
- Manage the whole picture: blood sugar, nutrition, sleep and not smoking all affect both your gums and your brain. If snoring or poor sleep is a concern, ask us about sleep apnea and airway dentistry.
- Help a loved one who needs it. If a parent or spouse is living with memory loss, daily brushing can slip. A gentle reminder, an electric toothbrush, or coming along to their dental visit can make a real difference.
How Forever Smiles Can Help
Healthy gums may contribute to a healthier body and potentially to a healthier brain.
Our comprehensive approach includes:
- Early detection of periodontal disease
- Advanced periodontal evaluations
- Professional cleanings and periodontal therapy
- Personalized home-care recommendations
- Oral bacterial testing, when appropriate
- Long-term monitoring of gum health to reduce chronic inflammation
This is what we mean by preventive dentistry that is Predictive, Preventive, Personalized and Participatory. We don’t just ask “how do we treat this?” We also ask “why did it happen and how do we keep it from coming back?”
Been away from the dentist for a while?
You are not alone, and you won’t be judged. Many of our patients come to us after years away, often because of a bad experience in the past. We understand dental anxiety. We listen first, we focus on your comfort, and we have the experience and technology to help you get healthy faster than you might expect.
Learn more about how we help anxious patients, including sedation options at our Glencoe office, or read our post Have You Been Avoiding the Dentist?
Frequently Asked Questions
Not as far as current research can prove. Gum disease is associated with a higher risk of cognitive decline and Alzheimer’s, and scientists are actively studying why. Treating gum disease is still worthwhile because it lowers chronic inflammation in your body.
No dental treatment can prevent Alzheimer’s disease. What we can do is help you control gum inflammation and keep your natural teeth, both of which research ties to healthier aging.
Bleeding when you brush or floss, red or swollen gums, bad breath that won’t go away, gums pulling away from your teeth, and teeth that feel loose. Gum disease is often painless in its early stages, which is why regular dental exams are important.
Studies show people with more missing teeth have a higher risk of cognitive decline and the risk grows with each tooth lost. In one large study, the link was not significant among people who had replaced missing teeth with dentures.
Keep routines simple and consistent, try an electric toothbrush, and help with brushing when needed. Bring them in for regular visits, and let our team know about their diagnosis so we can make each appointment calm and comfortable.
Protect More Than Your Smile
While no dental treatment can prevent Alzheimer’s disease, maintaining excellent oral health is one important way to reduce chronic inflammation and support your overall wellness.
At Forever Smiles, we believe in prevention. That’s because we know that by caring for your oral health today, you’re making an investment in your health for years to come.
Healthy Smiles. Healthier Lives. Call our Glencoe office at (320) 864-3129, find the Forever Smiles location nearest you, or start with a free video consultation from the comfort of your home.
Medically Reviewed by Dr. Shawn D. Knorr, DDS
This article was reviewed by Dr. Shawn D. Knorr, DDS, lead dentist at Forever Smiles, with 20+ years of experience helping patients in Glencoe, Arlington and Chanhassen protect their oral and overall health. This content is for educational purposes and is not a substitute for medical advice. If you have concerns about memory or cognitive changes, please talk with your physician.
References
- Alzheimer’s Association. 2026 Alzheimer’s Disease Facts and Figures.
- National Institute on Aging. Alzheimer’s Disease Fact Sheet.
- Chen CK, Wu YT, Chang YC. Association between chronic periodontitis and the risk of Alzheimer’s disease: a retrospective, population-based, matched-cohort study. Alzheimer’s Research & Therapy. 2017;9:56.
- Sparks Stein P, et al. Serum antibodies to periodontal pathogens are a risk factor for Alzheimer’s disease. Alzheimer’s & Dementia. 2012;8(3):196-203.
- Qi X, Zhu Z, Plassman BL, Wu B. Dose-response meta-analysis on tooth loss with the risk of cognitive impairment and dementia. JAMDA. 2021;22(10):2039-2045.
- Noble JM, et al. Serum IgG antibody levels to periodontal microbiota are associated with incident Alzheimer disease. PLoS ONE. 2014.
- Dominy SS, et al. Porphyromonas gingivalis in Alzheimer’s disease brains: evidence for disease causation and treatment with small-molecule inhibitors. Science Advances. 2019;5(1):eaau3333.
- Riviere GR, Riviere KH, Smith KS. Molecular and immunological evidence of oral Treponema in the human brain and their association with Alzheimer’s disease. Oral Microbiology and Immunology. 2002;17(2):113-118.
- de la Monte SM, Wands JR. Alzheimer’s disease is type 3 diabetes: evidence reviewed. Journal of Diabetes Science and Technology. 2008;2(6):1101-1113.
- Cortexyme Inc. GAIN Trial top-line results (SEC Form 8-K). October 2021.