Dental Hygiene May Play Significant Role in Cognitive Decline, Study Suggests

Effective dental hygiene practices may help to improve overall brain health, a new study published in Neurology indicates. The findings suggest that gum disease and tooth loss may be linked to brain shrinkage in the hippocampus, which is involved in memory and Alzheimer disease, according to the authors. They added that their research only shows an association and does not prove gum disease or tooth loss causes cognitive decline in Alzheimer disease.

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“Tooth loss and gum disease, which is inflammation of the tissue around the teeth that can cause shrinkage of the gums and loosening of the teeth, are very common, so evaluating a potential link with dementia is incredibly important,” said study author Satoshi Yamaguchi, PhD, DDS, of Tohoku University in Sendai, Japan, in a press release. “Our study found that these conditions may play a role in the health of the brain area that controls thinking and memory, giving people another reason to take better care of their teeth.”

The study notes that not all risk factors for dementia have been determined, with only 40% of all cases attributable to known modifiable risk factors. Recently, tooth loss and periodontitis caused by oral bacterial infection have been suggested as risk factors for Alzheimer disease and related dementia, according to the investigators.

“Regarding oral risk factors, animal studies have confirmed that a reduced number of teeth and the associated reduced masticatory activity cause hippocampal degeneration, and that the chronic oral administration of periodontal bacteria induces neurodegeneration in the hippocampus of wild-type mice,” the authors wrote in the study. “Previous studies in humans have reported the relationship between 1) the number of teeth, whole-brain volume, and gray matter volume (GMV); 2) the number of teeth and left hippocampal volume in older adults with cognitive impairment; and 3) people with edentulism and right hippocampus atrophy. However, these were cross-sectional studies. Although a longitudinal analysis recently reported that treatment of periodontitis improved AD-related brain atrophy, a previous study stated that the severity of periodontitis and tooth loss are not associated with morphological changes in the brain.”

To evaluate the potential association, the researchers enrolled 172 people with an average age of 67 years who did not have memory problems at study outset. The participants were given dental exams and memory tests at the beginning of the analysis, as well as brain scans to measure hippocampus volume both at the beginning of the study and 4 years later.

The investigators checked for gum disease via periodontal probing depth and recorded the number of teeth at the start of the study. The findings indicated that the number of teeth and amount of gum disease was associated with changes to the brain’s left hippocampus, according to the study.

Mild gum disease and fewer teeth were associated with a faster rate of brain shrinkage in the left hippocampus, whereas severe gum disease and having more teeth was associated with a faster rate of brain shrinkage in the same area, the authors found. After adjusting for age, the findings show that among individuals with mild gum disease, the increased rate of brain shrinkage due to 1 less tooth was equivalent to approximately 1 year of brain aging. Conversely, for people with severe gum disease, the increase in brain shrinkage due to 1 more tooth was equivalent to 1.3 years of brain aging.

“These results highlight the importance of preserving the health of the teeth and not just retaining the teeth,” Yamaguchi said in the release. “The findings suggest that retaining teeth with severe gum disease is associated with brain atrophy. Controlling the progression of gum disease through regular dental visits is crucial, and teeth with severe gum disease may need to be extracted and replaced with appropriate prosthetic devices.”

Additional research will be needed with larger patient populations to evaluate the findings, according to the study authors.

Reference

Yamaguchi S, et al. Associations of Dental Health With the Progression of Hippocampal Atrophy in Community-Dwelling Individuals: The Ohasama Study. Neurology. Jul 2023. Accessed July 17, 2023. DOI: 10.1212/WNL.0000000000207579; DOI: 10.1212/WNL.0000000000207579