One activity of daily living — oral hygiene, also including regular visits to the dentist — may play an important role in slowing cognitive decline as people age, according to new research published today in the Journal of the American Geriatrics Society.

“Clinical evidence suggests that the frequency of oral health problems increases significantly in cognitively impaired older people, particularly those with dementia,” said the paper’s first author, Bei Wu, Ph.D., of Duke University’s School of Nursing in Durham, NC. “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 look for a link between oral health and cognitive status, Wu and colleagues analyzed relevant cross-sectional (data collected at one specific point in time) and longitudinal (data collected over an extended period of time) studies published between 1993 and 2013. They say theirs is the first systematic review of studies focused on oral health and cognition.

Some of the studies examined by the researchers found that oral health measures such as the number of teeth, the number of cavities and the presence of gum disease were associated with an increased risk of cognitive decline or dementia. Others studies, however, were not able to confirm any such association. Also, findings based on the number of teeth or cavities are conflicting, according to the researchers, and limited studies suggest that gum disease and other conditions are associated with poorer cognitive status or cognitive decline.

Although oral hygiene and regular dental visits may help slow cognitive decline, existing research does not prove that one causes the other, Wu (pictured) said. “For future research, 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 said.

Results of another recent study, led by King’s College London and the University of Southampton, found that gum disease and cognitive decline are linked in people with early stages of Alzheimer’s disease.

The observational study, published in the journal PLOS ONE, found that the presence of gum disease at baseline was associated with a six-fold increase in the rate of cognitive decline in participants over the six-month follow-up period of the study. Gum disease at baseline also was associated with a relative increase in the pro-inflammatory state over the six-month follow-up period. The authors conclude that gum disease is associated with an increase in cognitive decline in Alzheimer’s disease, possibly via mechanisms linked to the body’s inflammatory response.