Understanding the Oral-Systemic Connection

A well-established link has been documented between periodontal disease and cardiovascular diseases like atherosclerosis, coronary heart disease, and acute coronary events, including myocardial infarction.^1-5 Meta-analyses have associated periodontal disease with elevated bacterial exposure, coronary heart disease, and early atherogenesis;⁵ a study in 2019 showed—for the first time—the common presence of bacterial DNA from viridans streptococci in aspirated thrombi of patients with acute ischemic stroke.⁶ The authors of this latter study conclude that Streptococcal bacteria, mostly of oral origin, may contribute to the progression and thrombotic events of cerebrovascular diseases.⁶ Other evidence suggests that oral health and systemic disease are indeed linked—what’s healthy for the mouth is also healthy for the rest of the body, and vice versa.^7-11

According to the 2000 US Surgeon General’s report, Oral Health in America, oral examinations can reveal signs and symptoms of more than 90% of systemic diseases.¹² However, despite this association, some researchers feel there is a lack of awareness in the healthcare community on their possible importance.¹² Nutrition-oriented physical exams, as taught in functional medicine, can help clinicians identify early warning signs of systemic disease. In the following video, IFM educator Michael Stone, MD, MS, identifies the signs to look for in the mouth during the patient physical exam:

There are approximately 800 species of bacteria that have been identified in the oral cavity, and periodontal disease is the most common oral condition in the population.¹⁴ In 2008, a systematic review found that periodontitis is a risk factor for coronary heart disease.¹⁵ One meta-analysis found that periodontal disease causes a 19% increase in the risk of cardiovascular disease.¹⁶ This increase in relative risk rises to 44% among individuals aged 65 years and over.¹⁶

In addition to cardiovascular diseases, some studies suggest that infections in the oral cavity are contributing factors in systemic inflammatory diseases such as diabetes.^7-9 New data suggest that this association is not indicated by traditional clinical signs of periodontal disease but rather by a cluster of host immune and inflammatory mediators.⁸ A 2015 study examining the relationship between periodontal microbiota and early diabetes risk found that higher levels of four species (A. actinomycetemcomitans, P. gingivalis, T. denticola, and T. forsythia) were associated with a two- to three-fold higher prevalence of prediabetes.¹⁷ The study speculates that if bacterial dysbiosis can contribute to prediabetes development in susceptible individuals, it may be possible that periodontitis and prediabetes (or diabetes) are comorbid conditions due to shared microbial risk factors.¹⁷

Researchers are calling for further studies into the possible causal associations between oral conditions and systemic disease.¹⁸ In 2018, the largest study to date of nearly one million people experiencing more than 65,000 cardiovascular events (including heart attack) found that after accounting for age, there was a moderate correlation between tooth loss (a measure of poor oral health) and coronary heart disease, yet when smoking status was considered, the connection between tooth loss and cardiovascular disease largely disappeared. The researchers concluded that the modest tooth loss–coronary heart disease gradient appeared to be explained by cigarette smoking.¹⁹