Mouth Infection: A Possible Onset of Alzheimer's

23 April, 2021
Infectious causes have always been suspected as the onset of some degenerative brain diseases. Some recent research points to a mouth infection as a possible cause of Alzheimer's disease. Find out more in this article.

A mouth infection as a possible onset of Alzheimer’s disease has been the news of several research studies published in the last year. In particular, an article in Science Advances links a bacterium in the oral cavity to the brains of Alzheimer’s patients.

Already in the last decade, scientific studies were pointing in the same direction. The microorganism most closely related is Porphyromonas gingivalis, a bacterium that gives rise to the oral disease we know as chronic periodontitis, which affects the gums.

What the researchers found was the same bacteria in the brains of deceased patients with Alzheimer’s disease. This postulates the hypothesis of a mouth infection as a possible onset of this disease.

Also, the research found gingipains in the same brains, which are toxic substances that these same bacteria produce. However, gingipains were also present in other brains of deceased people without Alzheimer’s disease.

What is Alzheimer’s disease?

Alzheimer’s disease is a type of dementia; it’s the most common of these forms of cognitive impairment in the adult population. Age and aging are risk factors for the disease, as a high prevalence has been detected in those over 65, and even more so in those over 85.

If a family member’s had Alzheimer’s disease, it’s more likely that, in the same family, there’s another member with the same condition. Genetics has been linked to this causality, and portions of DNA have even been identified as being altered in sufferers.

The possibility of a mouth infection as a possible cause of Alzheimer’s disease has always been a suspicion, beyond the other risk factors. The brains of those affected show inflammatory changes that are difficult to explain if they’re not attributed to an infectious microorganism.

The symptoms of the disorder tend to worsen over time. At first, there’s impairment of thought and language. Then memory is affected, with clear difficulties in recognizing names and persons. In a later stage, it becomes difficult to speak and, of course, to write.

Common symptoms at the end include an altered performance of common activities, such as brushing teeth, combing hair, or dressing. Also, there may be aggressiveness, which makes it difficult to approach and care appropriately.

A doctor talking to a patient with Alzheimer's.
Patients with Alzheimer’s disease progressively develop a number of changes besides memory loss.

Continue reading: Early Symptoms of Dementia: How to Detect Them

What is chronic periodontitis?

The mouth infection researchers identified as a possible cause of the onset of Alzheimer’s is chronic periodontitis. This is an inflammation of the gums which, if severe, destroys the supporting tissue of the teeth, causing them to fall out.

Not all periodontitis is the same, and its forms of presentation vary:

  • Common chronic: This is the most frequent of all. It’s rare in children and, if left untreated, will eventually lead to tooth loss. There have been cases of spontaneous improvement, but it can’t be ignored.
  • Progressive: Its evolution is very rapid, also leading to tooth loss. It has a familial genetic component that makes it more frequent among related individuals.
  • Necrotizing: This is the most aggressive form of periodontitis. The affected tissue dies because it doesn’t receive a proper blood supply. It’s much more common among people with immunity problems, such as those infected with HIV or those undergoing cancer treatments.
A mouth with chronic periodontitis.
Periodontitis causes inflammation of the gums and, if not treated in time, can lead to tooth loss.

Find out more: What Are the Kinds of Bacteria in Your Mouth?

Can a mouth infection be a possible onset of Alzheimer’s disease?

Recent studies have yet to clarify the answer to this question. Although clues are pointing in this direction, it would be imprudent to claim that there’s a direct link at this time.

In Alzheimer’s disease, the brain fills with proteins called amyloids. The amyloid plaques could be defense mechanisms of the organism against bacterial infections. Therefore, this opens the door to the possibility of bacteria as possible causes of the disease.

On the other hand, experts have already associated the bacterium P. gingivalis with other diseases of the body that don’t settle in the mouth. There’s an association with acute myocardial infarction and premature birth, for example.

On the flip side, we already know that Alzheimer’s patients are more prone to become infected with various microorganisms. The mouth, in particular, is a place where these patients suffer a lot, as their hygiene is deficient due to all the behavioral alterations they suffer from.

Therefore, caution has been the rule up to now. It’s possible that an infection in the mouth may initiate Alzheimer’s, but further confirmation is needed. For the time being, the direct cause is unknown and treatment remains palliative, not curative.

  • Tzeng, Nian-Sheng, et al. “Are chronic periodontitis and gingivitis associated with dementia? A nationwide, retrospective, matched-cohort study in Taiwan.” Neuroepidemiology 47.2 (2016): 82-93.
  • Vélez García, Iryna. “Asociación entre Porphyromonas gingivalis y enfermedad de Alzheimer. Revisión integradora.” (2019).
  • Silvestre, F. J., et al. “Neuroinflammation, Alzheimers disease and periodontal disease: is there an association between the two processes.” J Biol Regul Homeost Agents 31.2 Suppl 1 (2017): 189-96.