Alzheimer's and the Oral Microbiome

Will flossing actually improve your brain health?

Prior to the COVID-19 pandemic, the mouth was a long-forgotten part of the body. We took it for granted, not appreciating that similar to the gut, the mouth has its own microbiome and complex ecosystem. To this day, most people, dentists included, are unaware of the fact that an imbalanced oral microbiome paves the way for oral diseases such as decay and gum disease, as well as contributing to the development and severity of systemic diseases like diabetes, heart disease and Alzheimer’s.

With the unfortunate birth of COVID-19 came a silver lining: people started to see their mouths in a different way. They realized how important regular checkups at the dentist were. They also realized that their mouths were a home for viruses and bacteria and could be instrumental in the spread of infections. After all, the mouth is the gateway to the rest of the body. SARS-COV-2 was not the first virus to ever live in the mouth, just the most talked about.

The mouth as a gateway to the body

The idea of using the mouth or the saliva to test for diseases elsewhere in the body was something most people could also not fathom. Thanks to COVID-19, I am sure every single person reading this article has had their saliva collected for an emergency PCR test in the check-in area at Heathrow. It soon became apparent that the saliva that bathes the mouth harbours many bacteria, fungi, viruses, inflammatory markers and enzymes. Using this newfound knowledge, the scene of dentistry is rapidly changing, with many healthcare professionals looking at the mouth as an important piece of the puzzle for the ultimate goal of ‘full body health’. If we are able to see if someone has COVID-19 from their mouth- what else can we see?

Dental professionals also started to realise that the work they do in people's mouths to restore their function, eradicate infections, and stabilize oral disease has a domino effect on improving general health. Other healthcare professionals are also starting to realise that if they collaborate with dental professionals on treating a patient, the outcomes can be much better than if they were to work alone. For example, patients who suffer from chronic inflammatory diseases such as Rheumatoid Arthritis need to ensure that all infections or areas that may be harbouring inflammation in their body; are managed to improve their rheumatoid arthritis. Resolving a simple disease such as periodontal disease in the mouth can have a brilliant knock-on effect on reducing inflammatory markers generally in the body and improving systemic symptoms.

The research on the connection between the mouth and the rest of the body is now becoming more understood and acknowledged. Patients with gum disease are three times more likely to suffer from Diabetes Mellitus (Preshaw, 2012), three times more likely to be obese (Dahiya, Kamal, & Gupta, 2012), three times more likely to suffer from heart disease (Batty & et al, 2018), 70% more likely to develop Alzheimer’s Disease, (Beydoun & et al, 2020) and 2.85 times more likely to have erectile dysfunction.

The risk of Alzheimer's

The one connection that people seem the most shocked about is the connection between the mouth and Alzheimer's Disease. Alzheimer’s Disease is a disease that is currently a leading cause of mortality and morbidity globally (Vos, 2020). It presents as one of the greatest medical challenges that face this century due to its increasing prevalence worldwide and as yet, no effective treatment developed for it. The actual cause of Alzheimer’s is still unknown. Scientists believe that it is most likely caused by a combination of genetic, environmental and lifestyle factors. For example, people can possess an ApoE gene mutation which will increase their risk of developing Alzheimer’s, but this mutation is not solely responsible for causing it. It seems it is a combination of multiple risk factors that contribute to causing it in a person.

In 2019, Dominy et al published a paper claiming to have found one of the causative organisms related to Alzheimer’s Disease – Porphyromonas gingivalis (Dominy & et al, 2019). P gingivalis, to everyone’s surprise, also happened to be one of the keystone pathogens in chronic periodontal disease (aka gum disease). So how does an oral bacteria find its way to the brain?

The brain is approximately 9 inches away from the mouth, making it one of the brain’s closest neighbours. Dominy et al found that P gingivalis releases an enzyme called a gingipain which is neurotoxic and can travel up to the brain. Patients suffering from Alzheimer’s Disease had significantly higher levels of gingipains in their cerebrospinal fluid compared to healthy subjects. Furthermore, they found that in mice that had high levels of p. gingivalis, there was increased production of Aβ_1–42, a component of amyloid plaques. Amyloid plaques are thought to be one of the causes of Alzheimer’s as they disrupt cell communication in the brain. In Taiwan, they performed a retrospective cohort study on 18,672 citizens and found that having gum disease for over ten years was associated with a 70% increase in the risk of developing Alzheimer’s disease (Chang-Kai & et al, 2017).

If you’re still not convinced, a study published in the Journal of Alzheimer’s Disease (Beydoun & et al, 2020) further illustrated that there is a direct correlation between periodontal disease and Alzheimer’s Disease. The research looked at 6000 participants spanned over multiple age groups and followed them for up to 26 years. They performed dental examinations for gum disease as well as testing for bacteria and antibodies. The bacteria that seemed to be elevated in patients who went on to suffer Alzheimer’s disease was again, Porphyromonas ginigivalis.

Tooth loss and cognitive impairment

It doesn’t just seem to be bacteria that explain the link between the mouth and Alzheimer's disease. A study by NYU Rory Meyers College of Nursing in 2021 analyzed 14 studies on tooth loss and cognitive impairment, in over 34,074 adults. They found that adults with more tooth loss had a higher risk of dementia (1.28) and cognitive impairment (1.48). They also found that the more teeth were missing, the higher the risk of cognitive impairment grows (Xiang Qi, 2021). There are multiple hypotheses for this connection. One comes from the fact that with more teeth missing comes less ability to function and chew as well as a reduction in quality of life. This leads to people choosing to eat less nutritious foods and therefore potentially a loss of key nutrients to the brain. Another is the idea that if a patient suffers from gum disease, they will release high levels of oral inflammatory markers. These can travel around the body and cause inflammation elsewhere in the body, such as the brain.

So what can we do about it?

The most common form, late-onset Alzheimer’s, only manifests clinically at a late stage after a long period of clinically silent neurodegeneration. This means that you may have neurodegeneration and suffer from Alzheimer’s Disease, but with absolutely no signs or symptoms until it is too late. This is relatively similar to periodontal disease, where preclinical degeneration of the gums and surrounding bone occurs months before clinical signs of periodontal disease are present in the mouth. So if we can't see it clinically then why don’t we look for it subclinically? The use of biomarkers found in the saliva and blood is believed to be the answer to catching ‘silent’ diseases such as Alzheimer’s and periodontal disease early before irreversible destruction is visible/can occur (Hickman & et al, 2016).

Whilst I cannot argue to be a neuroscientist, I can argue that I am a dentist and should be pretty good at diagnosing periodontal disease. Having seen so many cases of periodontal disease somehow ‘slip through the cracks undetected’, I now strongly believe in using biomarkers such as enzymes related to collagen degradation (ammp8), microbiome testing, and testing of inflammatory markers in the saliva to assess a patient’s risk of gum disease and guide them back to health before destruction occurs. In the oral microbiome test, one of the oral bacteria that we look at is indeed, P. gingivalis. Therefore, through testing for gum disease, we are able to also flag up if a patient has high levels of P. gingivalis which may indicate gum disease and/or Alzheimer’s Disease.

Once we are able to see what is happening on a subclinical level, we can also personalize the patient’s oral care regime to ensure that their microbiome is guided back to equilibrium in the best way possible through personalized recommendations on what toothpaste, mouthwash, supplements and even foods they should be eating to positively shift their oral microbiome.

Victoria's Top Tips

1. Get your oral microbiome tested to see if you have heightened levels of P. gingivalis in your mouth
   If you do have high levels, go see a dentist to see how you can reduce levels of this through dental treatments such as Guided Biofilm Therapy and therapeutics like specific oral sprays and mouthwashes.Oral EcologiX™️
2. Use Propolis to keep P. gingivalis at bay
   Propolis is a natural substance produced by bees which has been clinically proven to treat periodontal disease and specifically kill p. gingivalis (Nansi, 2021)
3. Floss twice a day
   If you don’t floss, you are only doing 70% of the job. 30% of the bacteria resides between your teeth.
4. Swap your manual toothbrush for an electric one
   Scientists found that people who use an electric toothbrush have healthier gums, less tooth decay and also keep their teeth for longer, compared with those who use a manual toothbrush (Pitchika & et al, 2019)