Poor Oral Health May Raise Cognitive Decline, Dementia Risk

Batya Swift Yasgur, MA, LSW

September 13, 2022

Poor periodontal health and tooth loss may increase the risk for cognitive decline and dementia, new research suggests.

Results from a review of 47 studies showed that having periodontitis, tooth loss, deep periodontal pockets, or alveolar bone loss was associated with a 23% higher risk for cognitive decline and a 21% higher risk for dementia.

In addition, tooth loss alone independently increased the risk for cognitive decline and dementia by 23% and 13%, respectively. However, the overall quality of the evidence was low, the researchers note.

"A key point is that poor periodontal health is a modifiable risk factor; it can be addressed through self-care measures and regular use of basic oral health services, which may lower dementia risk to some extent ― although currently, we cannot say for sure how much," lead author Sam Asher, MPH, Institute of Dentistry, University of Eastern Finland in Kuopio, told Medscape Medical News.

The findings were published online September 6 in the Journal of the American Geriatric Society.

Past Evidence Insufficient

Periodontitis, defined as inflammation of tooth-supporting tissues, can lead to tooth loss. It is also known to be associated with several systemic conditions, such as diabetes and cardiovascular disease, but it has not been thoroughly studied in relation to cognitive decline or dementia.

The "available evidence on periodontal health and cognitive deterioration is insufficient and subject to limitations," the investigators write.

"Due to limited access to effective disease-modifying modalities, prevention of dementia through regimens targeting modifiable factors is paramount," Asher noted.

One such potential modifiable factor is periodontal health, which can be "maintained through self-care measures and regular use of basic oral health services," he said. This makes its potential relationship with cognition a "worthwhile area of research," Asher added.

The researchers scoured five electronic databases for relevant studies published until April 2022. Of 2132 articles, 47 met inclusion criteria and were included in the review. Of these, 24 were related to cognitive decline, and 23 were related to dementia.

To be included, a study was required to have a longitudinal design and a focus on a population without dementia at baseline. It had to have assessed periodontal health, including tooth loss, as an exposure and have cognitive decline and/or dementia as an outcome.

Unclear Mechanisms

For the studies of cognitive decline, the overall risk for bias was "high"; one study was of "moderate" quality; and 23 were of "low" overall quality. For dementia, the overall risk of bias was "moderate." Two studies were regarded as of "good" quality, nine as of "moderate" quality, and 12 as of "low" quality.

The studies with dementia as an outcome tended to include younger participants, have larger samples sizes, have longer duration, and have better exposure and outcome assessment.

Twenty studies reported a significant association between having at least one measure of periodontal health and cognitive decline. A higher risk was found for cognitive decline among participants with either low tooth count, a higher number of extracted teeth, periodontitis, deeper periodontal pockets, or alveolar bone loss.

In addition, 18 studies showed a significant association between at least one measure of periodontal health and dementia.

Poor periodontal health was associated with both cognitive decline (odds ratio [OR], 1.23; 95% CI, 1.05 – 1.38) and dementia (hazard ratio [HR], 1.21; 95% CI, 1.07 – 1.38).

Tooth loss was found to independently increase risk for cognitive decline (OR, 1.23; 95% CI, 1.09 – 1.39) as well as dementia (HR, 1.13; 95% CI, 1.04 – 1.23).

When the researchers stratified their analysis on the basis of extent of tooth loss, they found that partial tooth loss had a greater association with cognitive decline (OR, 1.5; 95% CI, 1.02 – 2.23), while complete tooth loss seemed to play a greater role in dementia (HR, 1.23; 95% CI, 1.05 – 1.45).

Potential Mechanisms?

Asher suggested several potential mechanisms that may account for the association between periodontal disease and cognitive decline. Periodontal inflammation "has been shown to increase systemic inflammation, which in turn may contribute to neuroinflammation, which is in itself a risk factor for dementia," he said.

Some previous research has suggested "that periodontal pathogens may have a direct effect on the brain, thus affecting cognition, although the exact mechanisms are currently unclear," Asher noted.

In addition, tooth loss may raise the risk of impaired cognition "due to resulting masticatory dysfunction and/or subsequent nutritional deficits," he said.

Asher noted that oral health problems "can be addressed through self-care measures and regular use of basic oral health services.

"Oral health professionals need to be particularly aware of early changes in periodontal health and oral self-care that often occur at older ages due to cognitive decline," he said.

Maintaining oral health is "perhaps even more important for people who already have some degree of cognitive decline or dementia, who often develop difficulties with maintaining oral hygiene," he added.

Bidirectional Association?

Commenting for Medscape Medical News, Bei Wu, PhD, Dean's Professor in Global Research and vice dean for research, New York University (NYU) Rory Meyers College of Nursing, pointed out that the studies that were included in the review were all observational and that there are "likely to be bidirectional associations between periodontal health and cognitive decline."

Wu is also an affiliated professor at NYU's College of Dentistry and the co-director of the NYU Aging Incubator. Although she was not involved with the current study, she conducted a similar review 3 years ago and found the association between tooth loss and cognitive decline to be "salient."

She called oral health "an essential element of healthy aging" and noted that healthcare professionals "can play an important role in educating patients and family members on the importance of improving oral health."

Moreover, "implementation of population-based oral health promotion programs and interventions have the potential to benefit a range of health issues, including cognitive health," Wu said.

Also commenting for Medscape Medical News, Percy Griffin, PhD, director of scientific engagement at the Alzheimer's Association, noted that "we have previously seen some data" linking periodontal disease and cognitive decline.

"However, the quality of the evidence is low, and the direction of causality is unclear," said Griffin. Thus, the findings, while "interesting," require more research, he added.

The study was funded by the Ella ja Georg Ehrnroothin Foundation, the Juho Vainion Foundation, the Minerva Foundation, the Päivikki ja Sakari Sohlbergin Foundation, the Suomen Aivosäätiö, Suomen Kulttuurirahasto, and the European Research Council. The investigators, Griffin, and Wu have reported no relevant financial relationships.

J Am Geriatr Soc. Published online September 8, 2022. Full article

Batya Swift Yasgur, MA, LSW, is a freelance writer with a counseling practice in Teaneck, NJ. She is a regular contributor to numerous medical publications, including Medscape and WebMD, and is the author of several consumer-oriented health books as well as Behind the Burqa: Our Lives in Afghanistan and How We Escaped to Freedom (the memoir of two brave Afghan sisters who told her their story).

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