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Gum disease’s link to Alzheimer’s disease.

March 02, 2019

You know you are getting old and sedentary when you start looking forward to the arrival of your favourite magazines, so you can sit with a good cup of coffee and read for a couple of hours.

The New Scientist is a great magazine and I really enjoyed this article, on new research, that looks at the possible (and probable) link between Gum Disease and Alzheimer’s.

The article describes the link as astonishing, but this is too strong a word as there is a link between gum disease and several systemic diseases including diabetes, cardiovascular disease, and pregnancy problems, but the link is unknown. Gum disease is an inflammatory disease and while it’s not thought that it is a direct causative link to these diseases, it’s known that these conditions will improve in a patient if their gums are healthy. As the American Surgeon General stated in a widespread health report, “ It is impossible to enjoy good general health without good dental health”.

Dementia is a crippling disease that has sky-rocketed as our population has aged, it robs otherwise healthy individuals and their families of a happy old age, and it now represents the fifth biggest cause of death worldwide.

There are many types of dementia but Alzheimer’s disease represents between 60 and 70 per cent of all cases. The vast majority of people with Alzheimer’s are diagnosed after 65 by patient history, cognitive tests and brain imaging, however, the only positive diagnosis is after death with the presence of two proteins called Amyloid and Tau being present in the brain. Although the symptoms strike mainly in the older ages we know these proteins start building up 15-20 years before extensive brain damage occurs.

Alzheimer’s is characterised by protein deposits of Amyloid and Tau, and the presence of these proteins on imaging is one of the earliest signs of the disease, so the theory was put forward that it was a faulty control of these proteins that lead to the disease. However, research into “Amyloid Theory” has not produced to any results and drugs produced to block or destroy the Amyloid and Tau proteins had a 99% failure rate. Furthermore, researchers also found many people in their 90’s with excellent cognitive function that also had significant deposits of the proteins.

In mice, it has been demonstrated that the brain will produce amyloid to protect itself from bacteria injected into the brain, it forms a sticky defence and eventually kills the microbes, and so researchers started to question the “Amyloid Theory”.

Research teams started to look at bacteria present in the brains of people who have suffered Alzheimer’s. Multiple laboratories working independently have identified Porphyromonas gingivalis as a microbe of extreme interest. It is the main bacterium involved in Gum Disease.

In mice genetically engineered to have Alzheimer’s, P.gingivalis invades and inflames the areas of the brain affected by Alzheimer’s. Gum Disease will produce and worsen the symptoms of the disease. P.Gingivalis was shown to actively invade the brain tissue of these mice.

P.Gingivalis uses two toxic enzymes called Gingipains to break down proteins and allow the P.gingivalis to feed on human tissue. These two enzymes were found in 96 per cent of 54 human Alzheimers’ brain samples. Gingipains were also found in higher levels in areas with Tau protein entanglement and the genetic material of P.gingivalis was also present in 100% of cases.

Further studies have looked at brain samples of elderly people who have died without Alzheimer’s’. Some had P.gingivalis and proteins but in much lower concentrations. It is already known that Amyloid and Tau can accumulate 10-20 years before the Alzheimer’s symptoms begin. Healthy mice infected with P.gingivalis will develop brain infection, amyloid production, tangles of Tau protein and neural destruction, in the regions of the brain normally affected by Alzheimer’s. All of this evidence points to causation and fulfils criteria that would allow attributing disease to a particular pathogen.

This is very exciting research but it is early days and there is a big difference between correlation and causation.

We already know that Gum Disease is an inflammatory disease and has correlation with a range of diseases. For instance, a diabetic patient will become more unstable if his gums become inflamed. Similarly, a diabetic patient is more likely to have gum disease, but clearing up one disease doesn’t cure the other. This is a correlation, not causation.

The observations of the human tissue and the experiments on the mice do strongly suggest a causative link. When healthy mice were given the P.gingivalis bacteria they developed symptoms that looked like human Alzheimer’s; when they were given drugs that either killed the bacteria or block the gingipains, there was a reduction in both symptoms and bacteria. Together these satisfy most of the conditions required to attribute a disease to a micro-organism.

There are strong hints that the same may be true in humans. Nearly all of the 54 Alzheimer’s brain sample contained gingipains, the more gingipains a person had, the more degraded Tau protein they had and the worse the Alzheimer’s symptoms were when alive.

Researchers have also found low levels of gingipains and damage in the brains of people who died without the condition, consistent with the fact that Alzheimer’s Disease is a result of years of accumulative brain damage.

Alzheimer’s Disease may be a complex disease and P.gingivalis may be the sole cause or one of a number of factors, but if the above research is borne out it could lead to a cure for Alzheimer’s. Researchers are now certain that the presence of amyloid and tau in the brain are responses to injury and not the initiator of the disease, which evidence now points to being a disease of infection and inflammation of the brain.

Companies are producing drugs to block gingipains and a vaccine against P.gingivalis. Current tests in mice are encouraging and are starting to move towards human trials, however, there are many things you can and should do to protect yourself against gum disease at the moment.

Gum disease, what is it?

Gum disease is an inflammatory process that starts off as mild gingivitis where the gums are inflamed and will bleed easily, this is caused by an accumulation of plaque (bacteria) on the teeth and gums leading to the bleeding.

In some people gingivitis, if left untreated, will lead to a more serious condition known as periodontitis, bone is progressively lost from around the teeth. This is not reversible and if not treated will lead to tooth loss. Some people will never progress to periodontitis and we feel there is a genetic link to the susceptibility of this disease. Other factors such as smoking, a poor diet, and poorly fitting fillings can also lead to the progression of bone loss.

How can I prevent gum disease?

Establish a good habit of brushing your teeth twice a day, along with cleaning between the teeth using dental sticks or interdental brushes to remove all the plaque. Adults should attend a hygienist every 6-12 months (or as recommended by your dentist) to remove any tartar/calculus that forms on the teeth.

If you smoke, STOP, cutting down doesn’t help you need to quit.

Gum disease is an inflammatory disease and so a good diet (cutting down on sugary processed foods) and a regular exercise regime will help to keep you healthy.

Stress also contributes to gum disease and as we know exercise helps people deal with stress.

If I have gum disease will I get Alzheimer’s?

We still don’t fully understand this disease, most adults have some degree of gum disease, but whether Gum Disease leads to Alzheimer’s is likely to depend on more than one factor. There may be a genetic link, it may depend on the severity of the gum disease, how many of a particular type of bacteria and how your body deals with the bacteria.

But the above advice of good brushing, a good diet, and regular exercise will help.

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