Oral health and 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?

15-20 mild Alzheimer's disease patients will be studied over 3 years. They will each be given a single standard length course of antibiotics followed by intensive dental treatment for at least a year to decrease oral bacteria at their source. Saliva tests (as mentioned above) and cognitive tests will be carried out before the treatment begins, at the end of the treatment, and 1 year following the end of the treatment. This information will be used to assess improvements in oral health and how well the patients can cope with keeping up good oral hygiene practices."

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.

Further information 

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.

With previous BRACE funding, Dr Shelley Allen has investigated neurotrophins and their receptors.