tooth loss and dementia

What’s the Link Between Diabetes, Loosing Teeth, and Cognitive Decline?

By | April 26th, 2023

Scientists are gaining ground on understanding the relationship between diabetes and cognitive decline or dementia. According to Dr. Bei Wu, the loss of teeth is also an important part of the story.

Studies show that people living with diabetes have a higher risk of developing cognitive decline or dementia during their lifetimes. In fact, the link between diabetes and dementia is strong, some researchers even call Alzheimer’s “type 3 diabetes.

Looking specifically at the connection between poor oral health and diabetes, researchers are now also studying the role tooth loss may play in the onset of cognitive decline in conjunction with diabetes. While good oral health is linked to lowering dementia risk, as a leader in studying oral health and cognitive decline, NYU’s Dr. Bei Wu is studying how each of these conditions overlap. 

In her latest study, Wu, Dean’s Professor in Global Health and Vice Dean for Research at the NYU Rory Meyers College of Nursing, and her team of researchers studied the link between diabetes and tooth loss regarding cognitive decline. Looking at 9,948 older adults 65 and older, the team found that the combination of diabetes and poor dental care contributes to worse cognitive function and faster cognitive decline. 

Known internationally as a leader in research on gerontology and aging, her research covers aging and global health topics, including oral health, long-term care, dementia, and caregiving. In particular, Wu is one of the first in the nation to study the link between oral health and cognitive decline in older adults. She sat down with Being Patient EIC Deborah Kan to discuss this latest research and what this study could mean for the future.

Being Patient: What’s the link between oral hygiene and brain health?

Dr. Bei Wu: If you have poor oral hygiene, most likely that will cause periodontitis. When you have a long-term kind of periodontitis, the outcome is tooth loss. Our team has been looking into this area of research, looking into poor oral health in relation to cognitive decline and dementia, for over 16 years. Increasing evidence suggests there’s a link that tooth loss is a potential risk factor for cognitive decline and potentially the onset of dementia. 

Being Patient: If you have lost a tooth, you obviously have a hole in your gums. Does that mean bacteria can actually get to our brains? Or what is the risk there?

Wu: There are several kinds of potential pathways to think about the linkages. Certainly, one is the bacteria, right? With tooth loss, it’s more so actually periodontitis, in that it is the bacteria that are causing the onset of periodontitis. This is one way that bacteria could potentially affect your brain function. This is one kind of hypothesis, and some bench scientists have found some of these linkages that certain bacteria deposited in your gums could potentially harm your brain. 

The second kind of hypothesis and pathway is linking nutrition intake. We know that once you have a higher number of tooth loss and limited functional teeth, that certainly will affect your nutrition intake. With nutrition, there are linkages between poor dietary intake that will affect your brain function. The third way is inflammation. That is a common kind of cause because that actually is also related to diabetes. Diabetes and poor oral health have one common link: inflammation. Both are causing higher levels of inflammation, which is related to poor brain function. 

The fourth kind of hypothesis links common chronic conditions like cardiovascular disease to diabetes and poor oral health. Strong evidence suggests that stroke has a very high risk of dementia. So, these are potential linkages and pathways. 

“Diabetes and poor oral health have one common link: inflammation.”

Being Patient: People with type two diabetes are at a much higher risk of getting dementia, and that makes sense because of glucose regulation. Glucose is very much the fuel for our brains, and if you have diabetes, it means that your glucose levels are off. However, is tooth loss a symptom of diabetes?

Wu: This is a very interesting question because in 2015, our team conducted a study that is actually very well cited and got a lot of media attention, and we used national data. It’s called the NHANES or the National Health and Nutrition Examination Survey, and it linked 40 years of data together from the 1970s to the 2010s. We surveyed individuals with diabetes in three major ethnic groups, Hispanic, Black, and White. Across these three groups, individuals with diabetes have twice the number of tooth loss compared to those without diabetes. 

It is a common kind of pathway as a potential inflammation because, for individuals who have diabetes, they do have higher levels of inflammation. But also, with tooth loss that’s caused by chronic periodontitis, your inflammation level is also high because of that. So ultimately, tooth loss is the outcome once you have long-term severe periodontitis. A dentist will let you know that, most likely, your tooth will fall out if you don’t take care of this. 

Being Patient: Talk to us about your latest study you published, which looked at the connection between tooth loss, diabetes, and dementia. What is the link?

Wu: We speculated that the common linkages are, again, inflammation and potentially higher linkages with nutrition intake. That’s because people with diabetes are more likely to have a poor kind of nutrition intake. So, you need to control your nutrition, but poor oral health affects your nutrition intake as well. Nutrition intake is one kind of common link, and you have inflammation as another link. Then, you also have cardiovascular diseases as a common link between these. Right?

We launched this study because poor oral health and diabetes are very common among older adults. We find that diabetes is a strong risk factor related to dementia in poor oral health, and now there’s increasing evidence to suggest this is a kind of a high risk of dementia. So, we looked at older adults’ potential to have multiple chronic conditions. It’s just not having just one condition, so we’re looking at comorbidity. For example, how is this co-occurrence of having poor oral health and a kind of diabetes, then jointly, what’s the impact on dementia? Right, and the cognitive decline? So that’s how we kind of start looking into whether there is any joint effect. 

From our study, we found that individuals with what we call edentulism, which means that you have complete tooth loss and diabetes, and jointly the combination of these is actually worse. They have a higher risk of cognitive decline than individuals with each condition alone. For example, if I only had diabetes, but I still have some teeth versus I still have some teeth, but I don’t have diabetes. 

We already have very strong evidence to suggest diabetes is a risk factor for dementia, but not so much for all poor kinds of oral health and tooth loss. We found in our study, actually, tooth loss and the complete tooth loss to even have a more accelerated decline of cognitive function than diabetes. That, I find it fascinating to think about, but tooth loss, we actually found to be a higher risk.

Being Patient: We’ve gotten some questions from the audience about getting teeth pulled and getting dentures already. Does having teeth pulled and having dentures put people at a higher risk of steeper cognitive decline if they’ve already been diagnosed?

Wu: Two years ago, we published a systematic review asking current findings on tooth loss and decline of cognitive function with mild cognitive impairment and dementia. It showed that adults with tooth loss, compared to no tooth loss, had a 48% higher risk of developing cognitive impairment and a 28% higher risk of being diagnosed with dementia. We also find that when you look at the dosage effect, for additional tooth loss each, for example, each additional missing tooth was associated with a 1.4% increase in the risk of cognitive impairment and a 1.1% increase in the risk of being diagnosed with dementia. Having said that, we also found, interestingly, that in individuals who have functional dentures, that the risk was not significant.

“We also found, interestingly, that in individuals who have functional dentures, that the risk was not significant.”

Being Patient: Interesting, because maybe, even if they’re not your real teeth, you have something filling that hole, and it’s less of a pathway. Right?

Wu: Correct. That’s why it’s a full public health kind of intervention to think about. It is important to have functional dentures. It’s also important because the underlying reasons that we speculate are true in function, right? So, truly in function if you have a good denture, could still be chewing better, and have a healthier nutrition intake, that potentially has an effect. Also, if you have a functional denture, you potentially have less inflammation in your mouth. So, that also can actually have some protective factors. 

But again, this is from our systematic review, and all these studies are conducted using observational study. So, I want to point out the caveats of this. So, don’t quote me to say, “Hey, this is like it’s a causal effect.” We need to be careful about this. It is all based on an observational study, and I want to say that there’s so much more research that needs to be done in this area that needs to have, for example, clinical trials run the ICT kind of studies to test this causal effect.

Being Patient: We have a question about the informational effect that you mentioned. Can you explain to people what you know, observational versus clinical? What’s the natural course for research to go next to really understand conclusively if some of these observational trials are substantiated?

Wu: Observational data versus clinical trials, right? So, in a clinical trial, what you could potentially do is to potentially introduce that your treatment group introduced these kinds of dental treatment, or like, improve oral hygiene. These kinds of interventions, then compared to this kind of care as a usual group, then you follow, for example, six months, or one year that you create, you could see some potential kinds of changes in terms of a cognitive function score. So, that is one way for these kinds of studies because you’re basically in this highly controlled environment. For a clinical trial, you introduce one kind of called active ingredient, then see how these ingredients work, then everything else stays the same. Versus observational studies that you have, you don’t introduce any kind of interventions. You just look at the data and see if there is any relationship between x and y.

That’s why, in longitudinal studies, you follow these individuals longitudinally so that you can see this kind of a time sequence and whether this one you control for this kind of early on. Then you look at what happened later on, like several years down the road, at how these individuals’ health outcomes change. So looking at it as kind of a predictor. It’s stronger than just a cross-sectional kind of study. 

This conversation has been edited for length and clarity.

Katy Koop is a writer and theater artist based in Raleigh, NC.

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