March 22, 2023

A healthy mouth may just help keep the brain healthy as well, new research out this week suggests. The study, a broad review of the existing evidence, found that poor dental health was linked to a later higher risk of cognitive decline and dementia. This increased risk was especially apparent for those missing some or all of their teeth.

Many studies have indicated that the health of our teeth and gums can influence the body elsewhere, including the brain. But other studies have been less conclusive, and there remains much uncertain about the strength and direction of this relationship. It’s possible, for instance, that the link can be explained by people developing poor dental health as a result of their early dementia, instead of the other way around—an example of something scientists call reverse causality.
In new research by a team from the University of Eastern Finland, they sought to conduct an updated meta-analysis of the evidence so far, one that would try to account for these gaps in knowledge. They collected and analyzed 47 longitudinal studies that tracked people’s oral and brain health over time, looking specifically at those who hadn’t been diagnosed with dementia at the start of the study.
Ultimately, they found that people with poor oral health were 23% more likely to eventually develop some amount of cognitive decline, and 21% more likely to develop dementia. And of the various measures of oral health studied, they also found that tooth loss in particular was independently associated with cognitive decline and dementia.
“Poor periodontal health and tooth loss appear to increase the risk of both cognitive decline and dementia,” the authors wrote in their paper, published Thursday in the Journal of the American Geriatrics Society.
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They caution that the evidence they examined is still limited and has many caveats, so it’s hard to draw firm conclusions. Many of the studies looked at different groups of people (some only included people over 65) or tracked them for different periods of time, while others may have had methodological problems in their design. But the authors say theirs is the largest review of its kind to date. They also tried to account for reverse causality in a separate analysis, and found that it could explain some but not all of the connection seen here.
In other words, while there might be a real cause-and-effect link between poor oral health and dementia, it will take more well-done research to better understand the specifics of this relationship, including the exact mechanisms behind it. Some scientists theorize, for instance, that the bacteria found in people with gum disease can help trigger or accelerate the complex chain of events that leads to dementia. The team behind this paper also notes that losing teeth could harm the aging brain by depriving people of familiar sensations. And there are likely other factors that can negatively affect both the mouth and brain at the same time, such as nutritional deficiencies.
Of course, keeping your mouth in good shape already has plenty of benefits, including for heart health. So even if there’s still a lot left to be studied here, it’s yet another reason to brush your teeth every day and to see a dentist regularly. The authors also point out that more has to be done to ensure that people can get access to good dental care throughout their lives.
“Given the impact of cognitive deterioration on periodontal health, oral health professionals are well-placed to track and intervene in early changes in periodontal health and oral self-care, but only if dental healthcare services are sustained over time and adequate oral health support is provided in the home setting when deterioration in self-care is identified,” they wrote.


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