Oral health is often somewhat overlooked when talking about dementia. Obviously, dental health is important but what is the relevance for dementia?
There is increasing scientific evidence showing that oral health can not only have an effect on general brain health but more importantly dementia progression and even mortality. Based on this, let’s have a look at the scientific evidence on how oral health impacts the development and progression of dementia.
Oral health is a commonly used generic term for any health-related issues in our mouth. The most common oral health issues during ageing are related to dental care. Many of us develop dental conditions the older we get, such as cavities or gingivitis (inflammation of the gums), which can lead to periodontitis – a more severe inflammation. It seems just part of ageing that such dental issues emerge, as our bodies are not as well at repairing oral tissue or dealing with inflammation.
These age-related oral health changes have led over the last decade to an increasing amount of studies investigating whether there is a link between dental health issues and dementia risk. In particular, there was an interest in whether periodontitis, a chronic inflammatory condition, has an effect on our future risk for dementia. The reason to investigate this was that chronic inflammation has been shown to increase our risk of dementia. For example, there is good evidence that other chronic inflammatory conditions, such as arthritis, have also shown that they can increase the risk of developing dementia in the future if left untreated. However, people with arthritis who are prescribed anti-inflammatory medication, such as ibuprofen type non-steroidal anti-inflammatories, show actually a reduced risk for dementia in the future. This shows that controlling inflammation in our body has an influence on the development of dementia.
What are the mechanisms which explain why inflammation increases our risk for dementia?
The short answer is that the exact factors are still being explored. Still, we know by now that inflammation is a key factor in the accumulation of proteins, such as amyloid and tau, which cause Alzheimer’s disease. There have been further suggestions that inflammation ‘fans the fire’ of these protein accumulations. This would mean if we have a chronic inflammatory process somewhere in the body it would speed up the protein accumulations, increasing, therefore, our risk for dementia. Vice versa, if we take anti-inflammatory medication, the protein accumulation will be slowed down, potentially reducing our risk for dementia. Now, before you rush to the bathroom cabinet and stuff yourself with ibuprofen, consider that taking medication if you do not have any inflammatory condition can create other health problems and even if you have a chronic inflammatory, please always discuss first with your doctor whether it is appropriate to take even such ‘over-the-counter’ medication long-term. The last thing we want to do is to reduce our long-term risk for one health conditions, such as dementia while increasing it for another condition.
What has this all to do with oral health, you might righlty ask?
The key to oral health is that dental health issues, such as periodontitis can also create chronic inflammatory conditions, which made researchers investigate whether there is a link between such conditions and dementia. The verdict so far, however, is pretty mixed. Some studies have found evidence that having chronic inflammatory oral conditions, such as periodontitis and gingivitis, increases our risk for dementia, while others have found no evidence in this direction. This has been confirmed by several systematic reviews, which review the evidence across studies, showing that there is no strong evidence that any such chronic inflammatory oral health conditions, increase our risk for dementia. In essence, the jury is still out as to whether oral health issues increase our risk for dementia in the long-term.
Happy days then, as we do not worry about our oral health and demenitia.
Not so fast. Yes, there is little scientific evidence so far to show the link between the risk of dementia and oral health, however, the scientific evidence of how our oral health is important once we have dementia, is much stronger.
The first aspect which is important to understand is that there is strong scientific evidence that once people have developed cognitive symptoms, they start to struggle to maintain appropriate oral health. There are various reasons for this, as for example, people might forget to clean their teeth/dentures or they might struggle to remember or perform the steps of cleaning their teeth/dentures appropriately. It should come, therefore, not as a surprise that scientific evidence shows that that overall oral and dental health in people with dementia is poorer than in people at a similar age without dementia. In particular, there is evidence that there is a higher incidence of dental caries, periodontal disease, increased pain, and other related dental problems in dementia.
A common approach to avoid such poor oral health is to have educational programs for people with dementia so that they learn how to take better care of their teeth or dentures. However, as anyone who knows a bit about dementia, the problem is that dementia is a progressive disease, which means that the cognitive problems will get worse over time, making it increasingly harder for the person with dementia to take part in educational programs. There has been, therefore, a shift over the last few years to develop more dental hygiene education programs for carers of people with dementia. Most of these programs are now targeted towards informal carers, but scientific evidence has shown that even a percentage of professional care staff are also not aware of the importance of oral health. Interestingly, there is also scientific evidence showing that even if informal carers were aware of the importance of good oral health for people with dementia, they were often reluctant to help with oral health.
Why is that?
The two main reasons given were that many people did not know how to clean someone elses teeth or dentures effectively and safely. The other reason was that challenging behaviour of the person with dementia made them more reluctant to help with their oral health. The good news is that there are now several well-proven educational programs/steps available for informal carers to help with oral health for people with dementia, even if they show challenging behaviour.
So, why is it important to maintain good oral health in dementia?
The most obvious reason is that oral health is always important, regardless of whether you have dementia or not. As anyone how had a tooth extracted can confirm, having a carious tooth can result in severe pain. Now, imagine that a person with dementia has such a carious tooth, while at the same time having significant cognitive deficits, which does not allow them to communicate anymore efficiently with their carer and family. The person with dementia very challenging, if not aggressive behaviour (and who wouldn’t?) if they have serious dental issues causing them pain. However, it is not only pain we should be concerned about, but also infection or inflammation caused either by a decaying tooth, periodontitis or gingivitis. We already know that inflammation can ‘fan the fire’ for dementia protein accumulation and this is certainly once we have dementia, where it can accelerate the disease progression. This means if we have an inflammatory oral health issue it can, in effect, speed up the development of the disease in the long-term.
But there are not only long-term issues as such infections and associated inflammation can also have short-term health consequences. If the infection and associated inflammation are brief but very severe, people with dementia can develop conditions such as delirium, which is a very serious health condition, resulting in rapidly deteriorating mental and physical health. Delirium leads in most cases to hospitalisation and in the worst cases even death and should be taken very seriously. Just imagine that such delirium could have started from a single infected tooth.
The final aspect of why oral health is so important in people with dementia is that it can even increase our risk of death significantly. We have already talked about delirium and how it can increase our risk of death but here we are talking about how oral health can lead more directly to death.
How is that possible?
To understand this, we have to do a slight digression and explore first what is the main cause of death for people with dementia in general. It might come as a surprise that for many people with dementia the cause of death on the death certificate will not state dementia, but more likely pneumonia. Pneumonia is quite common in later stages of dementia, as the disease has weakened the immune system in the person with dementia significantly, leading them to develop more often infections, such as pneumonia. For oral health, in particular, one type of pneumonia is very relevant – aspiration pneumonia.
What is aspiration pneumonia?
Aspiration pneumonia is a condition when getting food, fluids or saliva into our respiratory system by accidentally breathing them in (so-called aspiration). The most common form of aspiration pneumonia in dementia is when people with dementia develop swallowing problems in the latter stages of the disease. These swallowing problems can result in people with dementia accidentally getting food, fluids or saliva into their windpipe or even lungs. If the food, fluids or saliva are not removed from the respiratory system, it can potentially cause a significant infection, resulting in pneumonia. Many people are aware that such swallowing problems are to avoid in the latter stages of dementia, but what many people do not know is that our oral health plays a key role in whether such an aspiration event increases our chances of further disease progression or even death.
How can our oral health determine whether we will develop more severe aspiration pneumonia?
The reason is that the constellation of microbes in our mouth makes a big difference in the outcome of aspiration pneumonia. Several large-scale studies have found that people with specific, ‘foreign’ microbes in their oral cavity are at a higher risk of developing aspiration pneumonia. With ‘foreign’ microbes, I mean microbes that are usually not found in the oral cavity. At the moment it not clear whether these ‘foreign’ microbes come from the gut, for example via oesophageal reflux, which is highly common in late-stage dementia or from the external environment. Regardless, poor oral health leads to a proliferation of these ‘foreign’ microbes in the oral cavity, which is not their natural habitat. Importantly, the studies have found that developing aspiration pneumonia is more common in people who have these ‘foreign’ microbes in their oral cavity than people with dementia who don’t. It is, in my opinion, quite an astonishing finding that our oral health and associated microbial colonisation has potentially such a significant impact on us developing pneumonia in the latter stages of dementia, which in turn determines the progression of our disease or even our mortality.
Overall, the findings make clear that taking care of our oral health when we age remains critical. This is particularly true for people with dementia, who in the latter stages of the disease will unlikely be able to take care of their own oral health needs. Training for informal and professional carers on oral health can, therefore, make a significant difference. Not only will it avoid immediate oral and dental issues but also will determine long-term the progression of the disease.
Chew on that!