Oral Health and the Brain: The Link between Periodontitis and Alzheimer’s Disease

Have you ever laid comfortably in your bed and realized you have not brushed your teeth? It is a common scenario and while the temptation to stay in bed may be strong, the importance of maintaining good oral health goes beyond just freshening your breath. In fact, a connection between the most common oral condition, periodontitis, and Alzheimer’s has been proposed. In this blog, we will explore this connection and the compelling evidence behind it.
Frederika Malichová

Frederika Malichová

Neuroscientist at the University Of Cambridge.

An image of the brain and teeth as a puzzle.

Alzheimer’s disease

Alzheimer’s disease (AD) is an irreversible neurodegenerative disease affecting individuals in their sixties and above, and it is the most common form of dementia [1,2].

According to the NHS, the symptoms we observe in an individual affected by AD are difficulties with concentrating, general confusion of time and place, memory loss, as well as struggling to keep up with a conversation.

The major pathophysiological mechanism behind the symptoms is the synaptic and neuronal loss in the brain. This occurs due to the accumulation of proteins called amyloid Beta proteins and the subsequent accumulation of neurofibrillary tau tangles (an abnormal form of a protein called microtubule-associated tau)[1,2].

Although there are some drugs that are being tested to slow down cognitive decline, the disease still remains irreversible [3]. Recently, two immunotherapy drugs called Donanemab and Lecanemab promisingly showed to be slowing down cognitive decline by more than 20% [4, 5].

While the effects of the build-up are irreversible, and cognitive abilities are progressively declining, personalized intervention therapies to delay the onset of cognitive decline have been suggested. These include lifestyle interventions (exercise, social engagement), cognitive rehabilitation (memory training, problem-solving exercises), nutritional intervention, and more [6].

Periodontitis

Periodontitis is a chronic inflammatory disease caused by the accumulation of pathogenic bacteria located usually on our teeth below the gumline. The progress of periodontitis depends on the speed of the bacterial accumulation and there are different stages of the condition[7].

There are four stages determined by the severity of the disease based on clinical and radiographic findings: initial periodontitis, moderate periodontitis, severe periodontitis and advanced periodontitis [8].

Overall, it is the most common oral condition around 60% of the human population is affected by the disease in different severity [9]. The progress of periodontitis depends on the speed of the bacterial accumulation.

Recently, some researchers have proposed an intriguing link between periodontitis and Alzheimer's disease. We can use MediSearch to find out how these two seemingly unrelated conditions could be related.

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However, it is important to note that the proposed connection between AD and periodontitis has its limitations. In the studies, the researchers always point out connectivity of periodontitis with other diseases as well. For this reason, we will closely examine the scientific studies addressing this topic in the next section.

Diving Deeper: What Does Research Say about the Mind-Mouth Connection?

To begin, let us understand why researchers proposed the connection between oral health and AD in the first place. The reason is that multiple studies have discovered that in general, people with dementia have poor oral health, significantly fewer teeth and worse periodontal health [10].

According to a study by Mertande et al. [11] individuals suffering from AD showed a higher incidence of periodontal breakdown in comparison to healthy controls. The study assessed 58 individuals with AD and 60 cognitively normal adults for their periodontal health status. They found that the clinical periodontal parameters were higher in individuals with AD. Further, they also determined that the periodontal status of the diseased individuals worsens as the disease progresses from mild to
severe stage [11, 12].

However, these findings don't exactly imply that periodontitis is a risk factor for AD, but merely that AD patients have worse periodontal health. It turns out that the link between the two is more profound, and that periodontitis is indeed a risk factor for AD.

For example, a study comparing identical twins to determine the potential risk factors for dementia analysed a big cohort of 106 identical twins and discovered that tooth loss (which can be caused by periodontitis) before the age of 35 is a risk factor for AD [13].

A six-month observational study investigated whether the presence of periodontitis is related to the cognitive state. Individuals with mild to moderate periodontitis were linked to an increased cognitive decline in AD [14]. In particular, the presence of periodontitis was shown to increase the rate of cognitive decline by six-fold independent of the baseline cognitive state of an individual. Adding to that, a study conducted by Chen et al, showed that patients with chronic periodontitis for over 10 years have a 1.707–fold higher chance of developing AD later in life [15]. This highlights the importance of periodontitis prevention.

Prevention

Periodontitis is caused by the accumulation of bacterial plaque on the teeth and gums, leading to inflammation and damage to the supporting structures of the teeth.

Poor oral hygiene, smoking, genetic factors, certain systemic diseases (such as diabetes), and certain medications can increase the risk of developing periodontitis.

To prevent periodontitis, it is important to maintain good oral hygiene practices, including regular brushing and flossing, and visiting the dentist for professional cleanings.

Avoiding smoking and managing systemic conditions, such as diabetes, can also help reduce the risk of periodontitis [10, 15, 16 ].

Conclusion

The unexpected link between Alzheimer's and gum disease reminds us how different parts of our health are connected. It shows how looking after our teeth and gums isn't just about a good smile; it's vital for keeping our minds sharp as we age.

However, it is important to note that even though some studies suggest a possible link between periodontitis and AD, the exact mechanism behind this link is not known yet, and further research must be conducted. Nonetheless, periodontitis remains a risk factor for AD. So, the next time you contemplate staying in bed instead of brushing your teeth, remember that the simple act of oral hygiene may have profound implications for your cognitive health in the long run.

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Frederika Malichová

Frederika Malichová

Frederika is a postgraduate researcher at the University of Cambridge, where she investigates new biomarkers for Frontotemporal Dementia and other tauopathies. Her research has been published at prestigious conferences such as the Alzheimer’s Association International Conference 2023. She obtained her BSc in Biomedical Sciences from UCL, where she worked closely with the UK Dementia Research Institute.