A study in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring linked an imbalanced bacterial community in the oral microbiome to a biomarker for Alzheimer’s disease. Researchers said the association between the oral microbiome and AD was not linked to a single bacteria, but instead to an imbalance between good and bad.
“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,” said the study’s senior author Mony J. de Leon, EdD, professor of neuroscience in radiology and director of the Brain Health Imaging Institute at Weill Cornell Medicine. “Amyloid changes are often observed decades before tau pathology or the symptoms of Alzheimer’s disease are detected.”
The researchers studied 48 healthy, cognitively normal adults ages 65 and older. Participants underwent oral examinations to collect bacterial samples from under the gumline, and lumbar puncture was used to obtain CSF in order to determine the levels of amyloid beta and tau. To estimate the brain’s expression of Alzheimer’s proteins, the researchers looked for lower levels of amyloid beta (which translate to higher brain amyloid levels) and higher levels of tau (which reflect higher brain tangle accumulations) in the CSF.
Analyzing the bacterial DNA of the samples taken from beneath the gumline under the guidance of NYU College of Dentistry microbiologist Deepak Saxena, PhD, the researchers quantified bacteria known to be harmful to oral health (e.g. Prevotella, Porphyromonas, Fretibacterium) and pro-oral health bacteria (e.g. Corynebacterium, Actinomyces, Capnocytophaga).
The results showed that individuals with an imbalance in bacteria, with a ratio favoring harmful to healthy bacteria, were more likely to have the Alzheimer’s signature of reduced CSF amyloid levels. The researchers hypothesize that because high levels of healthy bacteria help maintain bacterial balance and decrease inflammation, they may be protective against Alzheimer’s. An association between gum bacteria and CSF tau levels. Future studies with larger sample sizes and longitudinal studies will need to be replicated for further investigation. While we wait, floss your teeth!