Study links oral microbiome to cognitive function in older adults

[Sly Saint]

The microbial ecosystems within our mouths may affect our cognitive function as we age, according to a study. Interventions such as prebiotics, including dietary nitrate, have potential for delaying cognitive decline.

About 15% of older adults have mild cognitive impairment, which is the largest risk factor for the development of dementia or Alzheimer's disease. There is a known association between periodontitis-gum disease-and worsened cognitive function. Researchers have identified two possible links between the mouth and the mind: pathogenic oral bacteria could enter the bloodstream and move to the brain, or pathogenic oral bacteria could displace nitrate-reducing bacteria, which help create nitric oxide the brain needs for synaptic plasticity and long-term potentiation. Anni Vanhatalo and colleagues characterized the oral microbiome of 115 participants, 55 of whom had mild cognitive impairment. Some participants had the apolipoprotein E4 (APOE4) allele, which increases risk for cognitive decline and Alzheimer's disease. A high relative abundance of bacteria in the genus Neisseria was associated with better executive function and visual attention within the mild cognitive impairment group. Among healthy participants, Neisseria correlated with working memory. High prevalence of bacteria in the genus Porphyromonas predicted mild cognitive impairment status, while Prevotella intermedia predicted APOE4-carrier status. According to the authors, diet can affect the oral microbiome, and a nitrate-rich diet (such as the Mediterranean and 'Dietary Approaches to Stop Hypertension' diets), favors bacteria associated with good cognitive outcomes.

Source:

PNAS Nexus

Journal reference:

L’Heureux, J. E., et al. (2025) Oral microbiome and nitric oxide biomarkers in older people with mild cognitive impairment and APOE4 genotype. PNAS Nexus. doi.org/10.1093/pnasnexus/pgae543.

Study links oral microbiome to cognitive function in older adults

 

[Jonathan Edwards]

I have never been that good at flossing but I can still do the Times crossword.

 

[Creekside]

People with better cognitive function probably have better oral hygiene practices, maybe more varied diet, and other such factors. People with cognitive decline might have their mouths open more, or swallow more or less often, which would affect the oral environment.

Claiming that gum disease causes cognitive decline makes for more dramatic headlines than claiming that cognitive decline leads to gum disease.

 

[Robert 1973]

I have never been that good at flossing but I can still do the Times crossword.

I didn’t have you down as a Times reader.

 

[Robert 1973]

“Dental flossing may lower the risk for incident ischemic stroke, cardioembolic stroke subtype and AF”: https://www.ahajournals.org/doi/10.1161/str.56.suppl_1.19

 

[Jonathan Edwards]

I didn’t have you down as a Times reader.

Oh I don't read the Times, I just tear off the crossword.

“Dental flossing may lower the risk for incident ischemic stroke, cardioembolic stroke subtype and AF”

Or it may be a marker of obsessive health monitoring and vegetarianism.

 

[Jonathan Edwards]

@Jonathan Edwards no doubt this is a load of tosh as well?

Sure is. Unless I am Rip van Winkel and I missed some of those decades.

 

[Sly Saint]

Red-flag symptom increases stroke and dementia risk - half of us have it

Good dental hygiene isn't just about a glowing smile. Developing positive oral health habits benefits your entire body.

Dr Catherine Tannahill, a dentist at Portman Dentex, explains there is so much more to oral health than pearly whites. "Our teeth act as a gateway to the body, so ensuring you have good oral hygiene means you avoid more serious health conditions," she said.

In fact, failing to keep your mouth healthy has some serious repercussions. "It's thought half the adult population has gum disease - the first sign is often bleeding gums, known as gingivitis - and studies have shown those with gum disease may be more likely to have a stroke," says Nyree Whitley, chief clinical officer at mydentist.

Experts have made the link between not enough tooth brushing and heart disease, she warns. "Research has shown people who have poor oral health or suffer from conditions such as gum disease or tooth loss are at increased risk of developing cardiovascular issues."

Bacteria that aren't effectively cleaned from your teeth, gums and tongue can make their way around your body in the bloodstream.

In 2023, a study by Aberdeen Royal Infirmary found that two-thirds of 160 people admitted with a heart attack had a severe gum infection. Nyree says: "In rare cases, inflammation from bacteria within your mouth can also lead to infection within the lining of your heart, which, over time, could cause clogged arteries."

If your dental health can affect your whole body, what other problems should we all be aware of?

Dementia: Academics have been working to establish a link between dental problems and dementia for some time. Professor Nicola West, who led the MySmile study at The Bristol Dental School, explains, "Recent studies suggest a clear association between dementia and poor oral health.

"A study has shown oral bacteria were four times more likely to be found in an Alzheimer's brain than a brain without the disease. Other studies have shown that periodontitis is associated with a sixfold increase in the rate of cognitive decline." Prof West has some positive news, however: "Evidence indicates that if gum disease can be stabilised, it might be possible to slow dementia disease progression.

"Because bleeding gums is a predictor of developing periodontitis, early detection and management is thought to prevent many cases of periodontitis before the effects become irreversible."

Red-flag symptom increases stroke and dementia risk - half of us have it

 

[Wonko]

So..the association is definately, don't brush teeth, leads to cognitive issues/dementia and not at all that people with cognitive issues or dementia may 'forget' to brush their teeth?

Coz they don't appear to have considered the later at all.

Not at all, in any way.....but then I suppose when your business is dentistry........

 

[perchance dreamer]

However the oral microbiome affects the rest of the body, it's important to have health gums and teeth if for no other reason than an unhealthy mouth can cause pain and lots of money spent at the dentist.

I've found I really need to floss as well as use an electric toothbrush and a Waterpik to remove the food remaining in my gums after flossing. I read somewhere that the gums are the gutters of the mouth, which, while gross, is also apt.

 

[Sly Saint]

Oral Dysbiosis and Autoimmunity: From Local Periodontal Responses to an Imbalanced Systemic Immunity. A Review

In the construction of explanatory models of the etiopathogenesis of periodontal disease, autoimmune mechanisms were among the first to be explored and historically, for more than five decades, they have been described in an isolated manner as part of the tissue damage process observed in periodontitis, however direct participation of these mechanisms in the tissue damage is still controversial. Autoimmunity is affected by genetic and environmental factors, leading to an imbalance between the effector and regulatory responses, mostly associated with failed resolution mechanisms. However, dysbiosis/infection and chronic inflammation could trigger autoimmunity by several mechanisms including bystander activation, dysregulation of toll-like receptors, amplification of autoimmunity by cytokines, epitope spreading, autoantigens complementarity, autoantigens overproduction, microbial translocation, molecular mimicry, superantigens, and activation or inhibition of receptors related to autoimmunity by microorganisms.

Although the microbiome is strongly involved in the maintenance of health and apparently in the control of autoimmunity, on the other hand, there is sufficient evidence in both humans (18, 19) and animals (20, 21) that supports the role of microorganisms in the occurrence of autoimmune responses. An expansion of pathobionts has recently been found in patients with autoimmune diseases and in animal models of autoimmunity (22).

The change in the characteristic microorganism communities of a particular microenvironment is known as dysbiosis, also called dysbacteriosis. Bacterial translocation, related to the pathogenesis of multiple diseases, could be better described as atopobiosis, which is the appearance of microorganisms that are characteristic of a certain microenvironment in the “wrong” place. Atopobiosis can occur by multiple ways (25, 26), and is perhaps one of the most relevant mechanisms in the participation of the oral microbiota in multiple conditions and diseases.

Oral Dysbiosis and Autoimmunity: From Local Periodontal Responses to an Imbalanced Systemic Immunity. A Review - PMC

(I'm not pretending to understand this paper but it raises a lot of issues about autoimmunity not necessarily in relation to periodontitis but the effect of dysbiosis in the microbiome which may be of interest.)

 

[jnmaciuch]

Also it’s completely ignoring the idea that a disease state can absolutely change the oral microbiome to begin with. Slight changes in salivary pH, or amylase enzymes brewing down sugars in saliva, or any number of other things can have profound affects on the microbiome makeup.

Someone can have obsessive oral hygiene but still have some underlying health issue that makes it way more likely for certain pathogenic bacterial species to take root unless they’re literally brushing and rinsing every half hour.

The paper itself doesn’t make any assertions that oral microbiome is solely dependent on hygiene behaviors, but of course any media coverage is going to take that spin to blame people for their own dementia.

 

[Trish]

That's a long video. Can you summarise what it says in a few words?