New research is the latest to suggest that the condition of our mouth and teeth is intimately connected to our brain health. The study found an association between people having severe gum disease or missing teeth in their early 60’s and an increased risk of them developing cognitive problems and dementia up to two decades later, compared to people with no gum disease.
The new study, published Wednesday in Neurology, looked at the medical history of over 8,000 middle-aged people who were taking part in another long-term research project meant to track their health over the rest of their lifetime. As part of the project, these volunteers underwent a full dental exam in their 60s (average age 63). At the time of this exam, none of them were considered to have dementia or mild cognitive impairment, a condition that often leads to full-blown dementia, including Alzheimer’s disease.
The researchers had followup data on this group of people for a median length of 18 years. About 19% of them overall developed dementia during that time. But there were clear differences between people who had varying gum disease severity. Among those who had already severe gum disease, 22% went on to have dementia, and 23% of those with no teeth in their 60s also eventually developed dementia. Meanwhile, 14% per cent of people without gum disease developed dementia.
When taking into account other risk factors, such as pre-existing conditions like diabetes or a history of smoking, the researchers estimated that having no teeth was associated with nearly double the risk of developing either dementia or mild cognitive impairment, compared to people with good gum health and no missing teeth. For those with severe gum disease and/or severe teeth loss, the risk was about 20 per cent greater. Those with only mild gum disease or little teeth loss appeared to have no significant added risk compared to the volunteers with the healthiest mouths, though.
Other studies similar in design to this one have found an association between gum disease and later dementia. But according to lead author Ryan Demmer, an epidemiologist at the University of Minnesota, this is one of the few to study people for such a long time and to include a large sample of African Americans. At the same time, these studies alone can’t show a direct cause-and-effect relationship between the two conditions. That’s not to say there isn’t a plausible connection, though.
Researchers have speculated that the chronic inflammation seen in gum disease can subtly influence our risk of many chronic illnesses, such as diabetes or stroke, which may in turn increase the risk of dementia. Others have suggested that the troublesome microbes found in diseased gums can even migrate to the brain and help trigger the formation of protein clumps that are characteristic of Alzheimer’s disease.
There are other reasons that could explain the study’s findings, however, according to Demmer. One important caveat, for instance, is that some people in the study may have already started to develop cognitive impairment, unnoticed at the time, before any dental problems could have had an effect. It’s also possible there are other hidden factors they didn’t account for that can raise someone’s risk of gum disease and dementia at the same time, making the link a coincidence rather than a true cause-and-effect.
“We need large studies that actually measure the underlying bacteria posited to be the risk factor of interest,” Demmer said, noting that many studies only tend to rely on an indirect measure of exposure to these bacteria, like a gum disease diagnosis. “We will also eventually need randomised controlled trials to see if treating periodontitis or preventing periodontitis [gum disease] prevents dementia.”
Still, there are already plenty of good reasons to keep your teeth and gums healthy for as long as possible, Demmer noted.
“At this time, improved oral health is not justified on the basis of cognitive health,” he said. “However, good oral health is important for overall health, and the potential for a side benefit of improved cognition over time is plausible.”