Dr Shelley Allen & Dr Debbie Shoemark - University of Bristol

Pilot Project: 2018 - 2019

Oral health and Alzheimer’s disease

See glossary at bottom of page for definition of underlined words.


Previous research has found that people who suffer from gum disease have a higher chance of developing Alzheimer's disease. One possible explanation for this incresed risk is the oral bacteria which are responsible for the gum disease. A previous BRACE-funded study (led by Dr Debbie Shoemark) has identified some types of oral bacteria associated with Alzheimer’s disease. This study looks to build on this work by conducting a feasibility study to see if sufferers of mild Alzhiemer’s disease are able to engage with good oral hygiene and whether this is economically feasible. This study may pave the way for an NHS funded trial into the effects of improved oral hygiene and the progression of Alzheimer’s disease.

What do we know?

It has been suggested that long-term bacterial infection results in an inflammatory cascade in the brain, which triggers or contributes to the development of Alzheimer’s disease. The source of this infection could be oral bacteria – many are able to evade the immune system, and there is an increased risk of developing Alzheimer’s disease in those with gum disease and poor oral hygiene.

What has been found out so far?

A BRACE-funded study led by Dr Debbie Shoemark identified some types of oral bacteria associated with Alzheimer’s disease in post-mortem brain samples of dementia patients. It remains to be answered if these bacteria were present in the brain during life, and if reducing levels of such bacteria in the brain (and at the source in the mouth) can benefit those with Alzheimer’s disease.

This study also established a saliva test which was able to identify whether or not a subject had gum disease. This was done by looking at the DNA content of a mouthwash swill. Those with gum disease had around 25 times more DNA in the swill than those without, due to the presence of a lot of bacterial DNA. This test can now be used as an indicator for how well oral hygiene treatments are reducing levels of bacteria.

The following publication provides a comprehensive background to the subject:

Shoemark, DK & Allen, SJ 2014, ‘The Microbiome and Disease: Reviewing the Links between the Oral Microbiome, Aging, and Alzheimer's Disease’. J Alzheimers Dis.

What next? - Feasibility study

The next step is to establish if patients with mild Alzheimer’s disease can engage and cope with the treatments, self-help and good oral hygiene protocol required to reduce oral bacteria - an obvious necessity if such treatments are to be effective. This study will be led by Dr Shelley Allen with Dr Debbie Shoemark, Professor Nicola West and her team from the Bristol Dental Hospital and Dr Liz Coulthard and team from the Memory Disorders Clinic. This will hopefully lead to an NHS funded trial to see if improved oral hygiene can slow down the progression of Alzheimer’s disease.

How will they do this?

In this first pilot study, up to 20 people with mild Alzheimer’s or vascular dementia or Mild Cognitive Impairment and with gum disease, will be treated at the Bristol Dental Hospital over a period of two years to improve the health of their gums and we will determine how easy it is for participants to achieve and maintain good oral hygiene. The participants will need to be accompanied by a project partner (for instance a friend or adult relation). Those interested should ring 0117 342 9637 at the Dental Hospital or email [email protected] and a member of the study team will provide more information and answer any questions.

Why is this important?

Compared to many other therapeutic approaches, improving oral hygiene could be a relatively simple and non-invasive task which does not require excessive contact time with clinical staff. It could therefore be used widely to prevent the onset or to slow the progression of Alzheimer's disease symptoms.


Inflammatory cascade – The series of biological processes (known collectively as a cascade) responsible for inflammation.
Immune system – The human body’s natural defence mechanism against pathogens (things that may harm the body).
Clinical trial – Trial to evaluate the effectiveness and safety of medications (or medical devices) by monitoring their effects on people.
Therapeutic treatment (therapeutic approach) – A treatment which is designed to reduce or reverse the symptoms of a disease.

Further information 

Poster of study

Please click here for more information about the work of Dr Debbie Shoemark.

Please click here for more information about the work of Dr Shelley Allen.

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