The risk factors for Alzheimer’s disease affecting more than 5.8 million Americans aren’t all in the brain. A new report from New York University highlights the connection between Alzheimer’s disease and Mouth bugs that fuel rogue proteins in the brain known as amyloid-beta.
It adds to growing evidence of a link between gum disease and the devastating mental illness.
The finding is based on dozens of older people. They underwent oral examinations and a lumbar puncture that collects cerebrospinal fluid (CSF).
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Those with more harmful than healthy gum bacteria were more likely to have signs of amyloid beta plaques.
The neuron destroying clumps trigger devastating memory loss and confusion.
Lead author Professor Angela Kamer, a dentist at New York University (NYU), said: “To our knowledge, this is the first study showing an association between the imbalanced bacterial community found under the gumline and a CSF biomarker of Alzheimer’s disease in cognitively normal older adults.
“The mouth is home to both harmful bacteria that promote inflammation and healthy, protective bacteria.
“We found having evidence for brain amyloid was associated with increased harmful and decreased beneficial bacteria.”
Alzheimer’s is believed to be caused by two proteins – amyloid beta and a second called tau which forms tangles in nerve cells.
Senior author Prof Mony de Leon, a neuroscientist at Weill Cornell Medicine, New York, said: “The mechanisms by which levels of brain amyloid accumulate and are associated with Alzheimer’s pathology are complex and only partially understood.
“The present study adds support to the understanding that proinflammatory diseases disrupt the clearance of amyloid from the brain, as retention of amyloid in the brain can be estimated from CSF levels.
“Amyloid changes are often observed decades before tau pathology or the symptoms of Alzheimer’s disease are detected.”
It is caused by inflammation with pockets between the teeth harbouring bacteria. Poor oral hygiene is the main cause.
The 48 participants aged 65 and over were healthy and cognitively normal. Bacterial samples from under the gumline and spinal amyloid beta and tau were measured.
Lower levels of amyloid beta translate to higher amounts in the brain amyloid levels while more tau in the fluid reflect accumulations of tangles.
Bad oral bacteria known to be harmful such as the species Prevotella, Porphyromonas and Fretibacterium were quantified along with good – such as Corynebacterium, Actinomyces, Capnocytophaga.
Individuals with an imbalance – with a ratio favouring harmful varieties – were more prone to the Alzheimer’s signature of reduced amyloid in CSF.
The researchers believe healthy bacteria protect against the disease by dampening inflammation.
Prof Kramer said: “Our results show the importance of the overall oral microbiome – not only of the role of ‘bad’ bacteria, but also ‘good’ bacteria – in modulating amyloid levels.
“These findings suggest that multiple oral bacteria are involved in the expression of amyloid lesions.”
There was no association between gum bacteria and tau levels. It remains unknown whether tau lesions will develop later or if the subjects will develop the symptoms of Alzheimer’s.
The researchers plan to conduct a longitudinal study and a clinical trial into improving gum health.
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They say “deep cleanings” to remove deposits of plaque and tartar from under the gumline may modify brain amyloid and prevent Alzheimer’s.
More than 900,000 people in the UK are living with dementia – a figure that will rise to two million by 2050 because of the ageing population.
With no cure in sight, there is an increasing focus on lifestyle interventions that could combat the crisis.
Medical experts say dental health is an essential part of your overall well-being. Poor oral hygiene has also been linked to heart disease, cancer and diabetes.
Maintaining healthy teeth and gums is a lifelong commitment. The earlier you learn proper habits – such as brushing, flossing and limiting sugar intake – the easier it is to avoid costly dental procedures and long-term health issues.
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The study is published in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring.