Oral health problems have been linked to disease elsewhere in the body.
According to the Mayo Clinic, poor oral health may contribute to heart disease, due to the spread of bacteria, while diabetes and HIV/AIDS can exacerbate oral health problems by reducing the body's resistance to infection.
As the older population continues to expand, oral health and cognition have become important areas of study, with researchers speculating that a common inflammatory pathway may hold the key to a link, if such a link exists.
The authors note that around 36% of people in the US aged over 70 years are living with some degree of cognitive decline. According to the Alzheimer's Association, around 5.4 million people in the US have Alzheimer's disease - the most common form of dementia.
The likelihood and severity of cognitive impairment and dementia tend to increase with age, and at the population level, they are expected to double by the year 2050.
At the same time, evidence suggests a higher rate of oral disease among older adults, significantly so among those with cognitive impairments and especially those with dementia.
Some evidence of a link with dementia
Researchers led by Dr. Bei Wu, of Duke University's School of Nursing in Durham, NC, wanted to know whether there was a link between oral health and cognitive status in older adults.
The team analyzed studies published between 1993-2013, using cross-sectional data, collected at a specific point in time, and longitudinal data, gathered over an extended period.
Results suggest that oral health measures, such as the number of teeth, the number of cavities and the presence of periodontal disease, or "gum disease," may reflect the risk of cognitive decline or dementia.
Some studies, however, did not reveal any association, and findings based on the number of teeth or cavities are conflicting. There is limited evidence of a link between periodontal conditions, such as gingivitis, and poorer cognitive status or cognitive decline.
The team also concludes that there is insufficient evidence to say that there is a common underlying cause in inflammation, or that there is any causative relationship between oral health and cognition.
Dr. Wu says:
"Clinical evidence suggests that the frequency of oral health problems increases significantly in cognitively impaired older people, particularly those with dementia. 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."
For future studies, the team suggests gathering data from larger, more representative population samples using standard cognitive assessments and oral health measures and more sophisticated methods of data analysis.
Medical News Today recently reported on research suggesting a link between gum disease and kidney disease.