Does Maintaining Oral Health Slow Cognitive Decline?

Megan Brooks

April 12, 2016

Maintaining good oral health may help slow age-related cognitive decline, but the exact relationship between oral health and cognitive status is unclear, according to results of the first systematic review of relevant research on the topic.

"There are some indications that some associations exist between cognitive function and oral health. However, the evidence is still weak at this point," Bei Wu, PhD, of the Duke University School of Nursing, in Durham, North Carolina, told Medscape Medical News. "More research needs to be done to further test the linkages between these two important health outcomes."

The study was published online April 1 in the Journal of the American Geriatrics Society.

Need for Better Data

But whether oral health and cognitive status in older adults are related and, if so, how is not entirely clear.

"Clinical evidence suggests that the frequency of oral health problems increases significantly in cognitively impaired older people, particularly those with dementia," said Dr Wu in a news release. "In addition, many of the factors associated with poor oral health — such as poor nutrition and systemic diseases like diabetes and cardiovascular disease — are also associated with poor cognitive function."

To investigate, Dr Wu and colleagues reviewed 56 studies published between 1993 and 2013 that assessed the association between oral health and cognitive decline. Of these studies, 40 were cross-sectional, and 16 were longitudinal. Of the 16 longitudinal studies, 11 examined the effect of oral health on change in cognitive health or dementia, and five examined the reverse.

Findings based on number of teeth or change in number of teeth or decayed teeth are conflicting or fail to reach statistical significance owing to small sample size, the authors report.

A limited number of studies showed an association between the presence of periodontal conditions (gingival health, pocket depth) and poorer cognitive status or cognitive decline, but other studies were unable to confirm any association.

The authors also note that although the notion that there is a common underlying cause associated with inflammation may be "enticing," it was examined directly in only one study and was found to be only marginally relevant.

"Current studies are not adequate to indicate whether poor oral health and cognitive decline have a common underlying cause in inflammation, but with the increase in major surveys with biomarker data, testing of this hypothesis is becoming more feasible," the authors write.

This systematic review "critically assessed" the current status of the literature and found that currently there is not enough evidence to conclude that a causal association exists between cognitive function and oral health, said Dr Wu.

Going forward, "we recommend that investigators gather data from larger and more population-representative samples, use standard cognitive assessments and oral health measures, and use more sophisticated data analyses," she added.

No Direct Relationship

This is an "important and highly relevant area of investigation," Anthony M. Iacopino, DMD, PhD, spokesperson for the American Dental Association, told Medscape Medical News.

"Given the aging of our population and the increasing prevalence of cognitive decline with advancing age, all healthcare professionals must be aware of factors that may adversely affect cognitive function and be prepared to work together to mitigate these factors when possible," said Dr Iacopino, of the University of Manitoba in Winnipeg, Canada.

On the basis of this systematic review, "there is not sufficient evidence at this time to definitively prove a causal association between oral health and cognitive function," he noted. "[But] it is important to understand that all systematic reviews have their own inclusion/exclusion criteria that determine which studies will be included in the analysis.

"There are likely to be many additional studies on this relationship in the future as well as additional systematic reviews. Additional research is likely to be more sophisticated and better able to determine if relationships exist between oral inflammation, systemic inflammatory burden, and cognitive status. It is possible that future studies and systematic reviews may point in a different direction, but for now, there is no conclusive evidence to support a direct relationship," Dr Iacopino concluded.

The study was supported by the National Institutes of Health. The authors and Dr Iacopino report no relevant financial relationships.

J Am Geriatr Soc. Published online April 1, 2016. Abstract

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