Gum Disease Bacteria Linked to Alzheimer’s Disease

Gum disease Alzheimer's

Gum disease has been linked to Alzheimer’s disease according to recent studies.

Alzheimer’s disease and other forms of dementia may be as simple as having gum disease. Shocked? Gum disease, also called periodontal disease, results from an oversize infection with a certain type of bacteria. This bacteria, according to researchers, damages nerves and brain cells to the point of memory loss.

This actually isn’t a new theory. Research has been connecting Alzheimer’s and other forms of dementia with gum and oral problems for a number of years. These studies have caused scientists to look more closely at the relationship.

What hasn’t worked for Alzheimer’s has been the different pharmaceuticals that have been developed for Alzheimer’s disease. Billions of dollars of public and private money has gone into this drug development research, with practically nothing to show for it in terms of viable solutions for a disease that causes as many as one in five deaths today.

The finding of a link between Alzheimer’s and gum disease bacteria opens the door for a Let’s review some of the research, beginning with the latest findings.

Bacteria enzymes flood Alzheimer’s brains

In a 2019 study from researchers at the University of California, University of Auckland, Harvard Medical School, and Cortexyme, researchers tested 54 brains1 of those who had Alzheimer’s, and compared these with normal brains.

Using two testing protocols, the researchers found that 96 percent and 99 percent of the hippocampus parts of the brains contained an enzyme called gingipains. Memories are generally stored in the hippocampus.

Gingipains is an enzyme produced by the gum disease bacteria Porphyromonas gingivalis. The bacteria use the enzyme to break down the body’s cell membranes, allowing them to invade the tissues.

When P. gingivalis invades the gums and oral cavity, they open up spaces between the teeth and gums and infect the teeth roots. They utilize this enzyme to help them gain entry into the gum tissues.

Scientists are not clear whether the gingipains directly harm the brain’s cells or whether the proteins that the body produces to combat the the bacteria enzymes damage the brain. Those proteins are often referred to as beta amyloids, which can cause fibrils and something called tau.

Previous research has linked the bacteria to cognitive difficulties, both in animal studies and human studies.
A number of studies have now linked cognitive decline and dementia to gum disease, which includes gingivitis and periodontal disease.

Dementia and dental health

In a large 2018 review of research from the UK’s King’s College London Dental Institut, researchers analyzed clinical studies and case-control studies that tracked dental health and dementia.2

The researchers found a clear link between the development of dementia and gum disease, along with poor dental health in general. The researchers concluded:

“The results suggest that poor oral hygiene is associated with dementia, and more so amongst people in advanced stages of the disease. Suboptimal oral health (gingivitis, dental caries, tooth loss, edentulousness) appears to be associated with increased risk of developing cognitive impairment and dementia.”

Blood vessels in the brain damaged

In a 2017 study, researcjers from King’s College found that gum diseases and pulmonary disease.4 This provides the link between dementia, because the blood vessels that feed the brain can become damaged by bacteria byproducts from the gums. This is because gum disease is also caused by an overgrowth of bacteria in the oral cavity.

Read more:  Dementia Linked to Gum Disease

To put it more bluntly: Bacteria produce an array of byproducts just like the rest of us. The problem is that unhealthy bacteria produce byproducts that can leak into our blood vessels through our gums. This can damage the blood vessels, especially those that feed the brain.

This mechanism was confirmed in a 2018 study from Germany’s University Medical Center Hamburg-Eppendorf.3 The researchers studied the relationship between chronic gingivitis and cerebral small vessel disease. The researchers found that periodontal disease not only increases the risk of damaging the blood vessels that feed the brain. Gum disease also increases the risk of stroke. The researchers concluded:

“The results suggest that periodontitis may be an emerging risk factor of small vessel disease-associated cerebrovascular disorders, and that the risk increase may be mediated by the systemic inflammation resulting from chronic oral infections.”

Other studies have linked cognitive decline to tooth decay and poor oral health.

Gum disease and cognitive decline

Other research has also linked gum disease to cognitive issues. For example, a study from the United Kingdom connected gingivitis and oral health to cognitive decline. The study’s findings are backed up by a multitude of research supporting the mechanisms.

Researchers from the Institute of Psychiatry at London’s King’s College followed over 1,050 adults for five years while tracking their oral health, as part of the Health, Aging and Body Composition (Health ABC) Study.5

The test subjects were given comprehensive cognition tests and periodontal examinations at the beginning of the study and each year following for five years. Their degree of periodontal disease – or lack thereof – was calculated together with parameters of cognitive decline.

Gingivitis scores were calculated using the oral examinations based on levels of gum inflammation and sensitivity – established through probing. Cognitive scores were calculated using the Modified Mini-Mental State examination – also referred to as 3MS.

The research found that 90% of the test subjects had declining cognition through year five. The researchers then matched and removed risk factors such as education, sex, race, heart disease, age and depression from the calculation.

The research found that higher gingivitis inflammation at year two was strongly associated with cognitive declines of more than five points in the third to fifth years.

Read more:  Tooth Loss Linked to Cognitive Decline

In their paper the researchers wrote, “Gingivitis is reversible, and periodontitis to some degree is preventable and controllable when manifest.”

oral probiotics gum disease

Reduce gum disease with oral probiotics.

Another study was done by researchers from the School of Dentistry at the University of Alabama. This study followed 9,853 adults over the age of 45 years old. They found that tooth loss was significantly associated with cognitive decline.

The research found that those who lost more than six teeth had greater cognitive decline than those with no tooth loss.

Gum disease and loss of teeth

While the association between cognition impairment and periodontal disease may seem mysterious, there is a solid basis for the mechanisms involved.

Numerous studies have linked periodontal disease with cerebrovascular disease and stroke. Cerebrovascular disease is the impairment of blood vessels that feed the brain cells. When these blood vessels become damaged or clogged, the brain can be starved of oxygen and essential nutrients.

A meta-study review of clinical research was conducted by medical researchers from Greece’s Attikon University Hospital.7 determined that 13 studies clearly proved the association between periodontal disease and a higher incidence of strokes and cerebrovascular disease.

Furthermore, medical scientists have established that pathogenic bacteria such as Streptococcus mutans that harbor within the gums will secrete biowaste products into the bloodstream and these waste products will damage blood vessels. Other research has suggested that some of these bacteria themselves may also escape into the bloodstream, causing sepsis and other infection-related disorders throughout the body.

A late 2011 study from the School of Dentistry at Italy’s University of Cagliari studied forty men between 20 years old and 40 years old.8 Half of the men had periodontal disease and the other half did not. The researchers tested the subjects for parameters indicating developing cardiovascular disease among both groups.

The research found that the periodontal disease patients had higher levels of inflammation-associated IL-2. This suggested to the researchers, “the existence of an early endothelial dysfunction in young adults with atypical periodontitis.”

In a study published in 2012, researchers from London’s University College School of Public Health combined mortality records with health surveys between 1995 through 2003.12 A sampling of nearly 13,000 people was used to calculate the cause of death and contributing factors.

This study found that those with tooth loss had three times the incidence of death related to having a stroke.

The association between stroke and cerebrovascular disease and cognition decline was made many years ago.1314

Periodontal disease is an inflammation of the gums produced by bacteria that colonize around the gums at the base and roots of the teeth. As the bacteria colonies grow, they form biofilms – which produce plaque. These bacteria biofilms secrete acids that break down the enamel of the teeth to form decay. These acids and other byproducts can also leak into the bloodstream, damaging the arteries that feed the brain.

Read more:  B Vitamins Slow Grey Matter Loss and Alzheimer’s Progression

Other research has found that orgal probiotics can significantly reduce gum disease.15


1. Dominy SS, Lynch C, Ermini F, Benedy M, Marczyk A, Konradi A, Nguyen M, Haditsch U, Raha D, Griffin C, Holsinger LJ, Arastu-Kapur S, Kaba S, Alexander Lee A, Ryder MI, Potempa B, Mydel P, Hellvard A, Adamowicz K, Hasturk H, Walker GD, Reynolds EC, Faull RM, Curtis MA, Dragunow M, Potempa J. Porphyromonas gingivalis in Alzheimer’s disease brains: Evidence for disease causation and treatment with small-molecule inhibitors. Science Advances 23 Jan 2019: Vol. 5, no. 1, eaau3333. DOI: 10.1126/sciadv.aau3333

2. Daly B, Thompsell A, Sharpling J, Rooney YM, Hillman L, Wanyonyi KL, White S, Gallagher JE. Evidence summary: the relationship between oral health and dementia. Br Dent J. 2018 Jan;223(11):846-853. doi: 10.1038/sj.bdj.2017.992.

3. Aarabi G, Thomalla G, Heydecke G, Seedorf U. Chronic Oral Infection and Cerebral Small Vessel Disease. Oral Dis. 2018 Jun 7. doi:10.1111/odi.12912.

4. Manger D, Walshaw M, Fitzgerald R, Doughty J, Wanyonyi KL, White S, Gallagher JE. Evidence summary: the relationship between oral health and pulmonary disease. Br Dent J. 2017 Apr 7;222(7):527-533. doi: 10.1038/sj.bdj.2017.315.

5. Stewart R, Weyant RJ, Garcia ME, Harris T, Launer LJ, Satterfield S, Simonsick EM, Yaffe K, Newman AB. Adverse oral health and cognitive decline: the health, aging and body composition study. J Am Geriatr Soc. 2013 Feb;61(2):177-84.

6. Cotti E, Dessì C, Piras A, Flore G, Deidda M, Madeddu C, Zedda A, Longu G, Mercuro G. Association of endodontic infection with detection of an initial lesion to the cardiovascular system. J Endod. 2011 Dec;37(12):1624-9.

7. Sfyroeras GS, Roussas N, Saleptsis VG, Argyriou C, Giannoukas AD. Association between periodontal disease and stroke. J Vasc Surg. 2012 Apr;55(4):1178-84.

8. Cotti E, Dessì C, Piras A, Flore G, Deidda M, Madeddu C, Zedda A, Longu G, Mercuro G. Association of endodontic infection with detection of an initial lesion to the cardiovascular system. J Endod. 2011 Dec;37(12):1624-9

9. Chandra RV. Re: Association between periodontitis and hemorrhagic stroke among Koreans: a case-control study. J Periodontol. 2011 Nov;82(11):1521

10. Yoshida M, Murakami T, Yoshimura O, Akagawa Y. The evaluation of oral health in stroke patients. Gerodontology. 2012 Jun;29(2):e489-93.

11. Zoellner H. Dental infection and vascular disease. Semin Thromb Hemost. 2011 Apr;37(3):181-92.

12. Matthews JC, You Z, Wadley VG, Cushman M, Howard G. The association between self-reported tooth loss and cognitive function in the Reasons for Geographic And Racial Differences in Stroke study: an assessment of potential pathways. J Am Dent Assoc. 2011 Apr;142(4):379-90.

13. Ghizoni JS, Taveira LA, Garlet GP, Ghizoni MF, Pereira JR, Dionísio TJ, Brozoski DT, Santos CF, Sant’Ana AC. Increased levels of Porphyromonas gingivalis are associated with ischemic and hemorrhagic cerebrovascular disease in humans: an in vivo study. J Appl Oral Sci. 2012 Feb;20(1):104-12.

14. Watt RG, Tsakos G, de Oliveira C, Hamer M. Tooth loss and cardiovascular disease mortality risk–results from the Scottish Health Survey. PLoS One. 2012;7(2):e30797.

15. Adams C. Oral Probiotics: Fighting Tooth Decay, Periodontal Disease and Airway Infections Using Nature’s Friendly Bacteria. Logical Books, 2016.

Case Adams, PhD

Case Adams has a Ph.D. in Natural Health Sciences, is a California Naturopath and is Board Certified as an Alternative Medicine Practitioner, with clinical experience and diplomas in Aromatherapy, Bach Flower Remedies, Blood Chemistry, Clinical Nutritional Counseling, Homeopathy and Colon Hydrotherapy. He has authored 27 books and numerous articles on print and online magazines. Contact: [email protected]

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