September 20, 2023
Need more incentive to brush and floss? A new report shows that good dental health is linked to better brain health.
The study, published in Neurology, found that gum disease and tooth loss were associated with shrinking in the hippocampus, a part of the brain critical for memory and learning and one of the first areas to be damaged by Alzheimer’s disease. The study was small, involving 172 older men and women who were living in Japan. But the findings build on earlier evidence that gum disease is tied to an increased risk for Alzheimer’s disease and other forms of dementia.
“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, of Tohoku University in Sendai, Japan. “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.”
For the research, the investigators looked at men and women without serious memory problems whose average age was 67 when the study began. At the outset, they all had dental exams. The researchers evaluated them for gum disease by measuring “pockets,” or the loss of gum tissue around the teeth. Periodontal probing depths of one to three millimeters around the teeth were considered healthy; probing depths of three or four millimeters in several tooth areas indicated mild gum disease; and severe gum disease was determined by probing depths of five or more millimeters in several areas, indicating the greatest degree of bone loss at the base of the teeth. The researchers also checked whether participants had any loose or missing teeth.
In addition, those in the study completed tests of memory and thinking skills and underwent brain scans to measure the volume of the hippocampus at the study’s start. Dental exams and brain scans were repeated four years later, at the end of the study.
The researchers found that people with mild gum disease who had fewer healthy teeth had more shrinkage in the left hippocampus. The increase in the rate of brain shrinkage with the loss of one tooth, on average, was equivalent to nearly one year of brain aging.
For people with severe gum disease, tooth loss did not correlate with brain shrinkage. But having severe gum disease, despite keeping one’s teeth, wobbly as they may be, was associated with brain shrinkage 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,” Dr. Yamaguchi said. “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.”
The findings build on earlier studies linking poor dental health to an increased risk of Alzheimer’s disease. One large study from the University of Minnesota looked at 8,275 middle-aged men and women living in four parts of the United States over a 20-year period. It found that those with the most severe gum disease at the study’s outset had about twice the risk of developing dementia or mild cognitive impairment, a brain disorder that can progress to full-blown Alzheimer’s disease, over the study period. In that study, those with minimal tooth loss and mild gum disease were no more likely to develop memory problems or dementia than those with healthy teeth.
Another study of twins from Sweden found that if one twin developed severe gum disease and missing teeth before age 35, that twin was four to five times more likely to develop dementia years later than their sibling without dental disease. Further, in those with early Alzheimer’s disease, gum disease has been linked to a faster rate of cognitive decline, research shows.
These studies show only an association between dental health and brain health and cannot prove cause and effect. But other studies have found that people who die with Alzheimer’s disease are more likely to have bacteria linked to gum disease present in their brain than those who didn’t have Alzheimer’s disease. It is possible that bacteria in the mouth could travel to the brain, causing damage there. Gum disease is also tied to body-wide inflammation, which may damage blood vessels throughout the body, including in the brain. Indeed, higher levels of inflammation have been linked to various chronic diseases of aging, including Alzheimer’s disease.
The takeaway is that good oral hygiene is important for all of us, and not just for a shiny smile. Regular flossing and brushing of teeth may help to keep the brain in good working order.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D. Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Satoshi Yamaguchi, Takahisa Murakami, Michihiro Satoh, et al: “Associations of Dental Health With the Progression of Hippocampal Atrophy in Community-Dwelling Individuals
The Ohasama Study.” Neurology, September 5, 2023