Tooth Loss and Diabetes Together Hasten Mental Decline

Miriam E. Tucker

March 22, 2023

Both tooth loss and diabetes can lead to accelerated cognitive decline in older adults, most specifically in those 65 to 74 years of age, new findings suggest.

The data come from a 12-year follow-up of older adults in a nationally representative US survey.

"From a clinical perspective, our study demonstrates the importance of improving access to dental healthcare and integrating primary dental and medical care. Healthcare professionals and family caregivers should pay close attention to the cognitive status of diabetic older adults with poor oral health status," lead author Bei Wu, PhD, of New York University (NYU), told Medscape Medical News. Wu is the Dean's Professor in Global Health and co-director of the NYU Aging Incubator.

Moreover, said Wu: "For individuals with both poor oral health and diabetes, regular dental visits should be encouraged in addition to adherence to the diabetes self-care protocol." 

Diabetes has long been recognized as a risk factor for cognitive decline, but the findings have been inconsistent for different age groups. Tooth loss has also been linked to cognitive decline and dementia, as well as diabetes.

The mechanisms aren't entirely clear, but "co-occurring diabetes and poor oral health may increase the risk for dementia, possibly via the potentially interrelated pathways of chronic inflammation and cardiovascular risk factors," Wu said.

The new study, published in the Journal of Dental Research, is the first to examine the relationships between all three conditions by age group.  

Diabetes, Edentulism, and Cognitive Decline

The data came from a total of 9948 participants in the Health and Retirement Study (HRS) from 2006 to 2018. At baseline, 5440 participants were aged 65-74 years, 3300 were aged 75-84, and 1208 were aged 85 years or older.

They were assessed every 2 years using the 35-point Telephone Survey for Cognitive Status, which included tests of immediate and delayed word recall, repeated subtracting by 7, counting backward from 20, naming objects, and naming the president and vice president of the US. As might be expected, the youngest group scored the highest, averaging 23 points, while the oldest group scored lowest, at 18.5 points.

Participants were also asked if they had ever been told by a doctor that they have diabetes. Another question was: "Have you lost all of your upper and lower natural permanent teeth?"

The condition of having no teeth is known as edentulism.

The percentages of participants who reported having both diabetes and edentulism were 6.0%, 6.7%, and 5.0% for those aged 65-74 years, 75-84 years, and 85 years or older, respectively. The proportions with neither of those conditions were 63.5%, 60.4%, and 58.3% in those three age groups, respectively (P < .001).

Compared with their counterparts with neither diabetes nor edentulism at baseline, older adults with both conditions aged 65-74 years (P < .001) and aged 75-84 years had worse cognitive function (P < .001).

In terms of the rate of cognitive decline, compared to those with neither condition from the same age cohort, older adults aged 65-74 years with both conditions declined at a higher rate (P < .001).

Having diabetes alone led to accelerated cognitive decline in older adults aged 65-74 years (P < .001). Having edentulism alone led to accelerated decline in older adults aged 65-74 years (P < .001) and older adults aged 75-84 years (P <  0.01).

"Our study finds the co-occurrence of diabetes and edentulism led to a worse cognitive function and a faster cognitive decline in older adults aged 65 to 74 years," say Wu and colleagues.

Study Limitations: Better Data Needed

The study has several limitations, most of them due to the data source. For example, while the HRS collects detailed information on cognitive status, edentulism is its only measure of oral health. There were no data on whether individuals had replacements such as dentures or implants that would affect their ability to eat, which could influence other health factors.

"I have made repeated appeals for federal funding to collect more oral health-related information in large national surveys," Wu told Medscape Medical News.

Similarly, assessments of diabetes status such as A1c were only available for small subsets and not sufficient to demonstrate statistical significance, she explained.

Wu suggested that both oral health and cognitive screening might be included in the "Welcome to Medicare" preventive visit. In addition, "Oral hygiene practice should also be highlighted to improve cognitive health. Developing dental care interventions and programs are needed for reducing the societal cost of dementia."

The study was partially supported by the National Institutes of Health. The authors have reported no relevant financial relationships.

J Dent Res. Published March 12, 2023. Full text

Miriam E. Tucker is a freelance journalist based in the Washington, DC, area. She is a regular contributor to Medscape, with other work appearing in The Washington Post, NPR's Shots blog, and Diabetes Forecast magazine. She is on Twitter: @MiriamETucker.

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