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 the 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.

Published in the journal PNAS Nexus, 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.

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PNAS Nexus