3 minute read

Periodontal Disease & Alzheimer's

Recent news reports have suggested that an infection initiated by a bacterium found in the oral cavity could be a predisposing factor or an initiator of Alzheimer’s disease. The Bulletin takes a closer look at the evidence

By Margaret Galvin

Alzheimer’s disease (AD) is the most common type of dementia, causing problems with memory, thinking, and behaviour. Dementia affects approximately 160 000 Australians, with Alzheimer’s disease accounting for 50-75% of dementia cases. The most important risk factor of Alzheimer’s disease is the increase of age. Other predisposing factors thought to contribute to Alzheimer’s include genetics, chromosomal factors, diet, and aluminium.

As you may well know, periodontal disease is an inflammatory disease which affects the soft and hard structures that support the teeth, or as I tell my patients, it is a disease that destroys the structures that help hold your teeth in your head! Porphyromonas gingivalis (P. gingivalis), the pathogen which contributes to the pathogenesis of Chronic Periodontitis, has been found in the brains of deceased Alzheimer’s patients. Could it be that periodontal disease is also a predisposing factor or an initiator of Alzheimer’s disease?

The Science

The following is what researchers have found through one particular scientific study – Ilievski, V. Zuchowska, PK. et al 2018:

• 10 mice in a study group were exposed orally to P. gingivalis over 22 weeks and another 10 mice were in a control group n Brain tissue health was studied in both groupsafter 22 weeks

• Significantly higher amounts of accumulated amyloid beta (peptides found in the plaques of brains affected by AD) was found in the study group n Increased brain inflammation and fewer intact neurons due to degeneration were also found in the study group n DNA of the bacteria was found in the brain tissue of the study group

• Bacterial protein was noted inside their neurons.

“ Researchers state their results strongly suggest that chronic oral infection of P. gingivalis can be an initiator of the development of neuropathology that is consistent with that characteristic of Alzheimer’s disease in humans”

• Researchers state their results strongly suggest that chronic oral infection of P. gingivalis can be an initiator of the development of neuropathology that is consistent with that characteristic of Alzheimer’s disease in humans

Another study – Dominy, Lynch, Ermini, Benedyk et al 2019 – found the following: n The analysis of brain tissue, spinal fluid, and saliva from AD patients (both living and deceased) found evidence of P. gingivalis n Gingipain (a protease secreted by P. Gingivalis) was shown to be neurotoxic to Tau (a protein needed for normal neuronal function) n It is thought the P. gingivalis and/or its product gingipain travel to the brain and acts in AD pathogenesis to promote neurone damage

• The presence of P. gingivalis increased the production of amyloid beta, a component of the amyloid plaques, whose build-up contributes to Alzheimer’s disease

• Small-molecule inhibitors were designed and synthesised targeting gingipains to block neurotoxicity n The inhibition of gingipain reduced the bacterial load of an established P. gingivalis brain infection, blocked amyloid beta production, reduced neuroinflammation, and rescued neurons in the hippocampus (the part of the brain thought to be the centre of emotion, memory, and the autonomic nervous system)

• The researchers state “Our identification of gingipain antigens in the brains of individuals with AD and also with AD pathology but no diagnosis of dementia argues that brain infection with P. gingivalis is not a result of poor dental care following the onset of dementia or a consequence of late-stage disease, but is an early event that can explain the pathology found in middle-aged individuals before cognitive decline”

However, Dr David Reynolds, the Chief Scientific Officer from Alzheimer’s Research UK, states that:

“While some studies have found higher levels of bacteria in the brain during Alzheimer’s, it has been difficult to tell if they have played a direct role in the development of the disease. We know diseases like Alzheimer’s are complex and have several different causes, but strong genetic evidence indicates that factors other than bacterial infections are central to the development of Alzheimer’s, so these new findings need to be taken in the context of this existing research.

“ While some studies have found higher levels of bacteria in the brain during Alzheimer’s, it has been difficult to tell if they have played a direct role in the development of the disease”

Dr David Reynolds Chief Scientific Officer, Alzheimer’s Research UK

Maintaining good dental health is an important part of a healthy lifestyle, and while we don’t yet fully know the extent to which it can affect our dementia risk, the presence of a single type of bacteria is extremely unlikely to be the only cause of the condition.”

What does all this mean for oral health professionals?

We should all be keeping an eye on the developing literature on this subject as it comes to light and sharing it with our colleagues for discussion. I also think it provides an opportunity to reiterate to our patients that they can do so much for their general health by taking their oral health seriously.

The information provided in this feature was acquired from the sources referenced below and has been published to raise awareness of these research finding. This article does not serve as a substitute for a journal research article. We encourage further research by readers and if you find anything else of interest about the topic, please feel free to share it by writing to the editor at bulletin@dhaa.info.

This article is from: