Despite popular belief, periodontal disease has not been proven to cause atherosclerotic heart disease or stroke, and treating periodontitis has not been proven to prevent heart disease or stroke, according to a statement published today in Circulation.
The statement, authored by the American Heart Association (AHA) Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease, found no conclusive scientific evidence that periodontal disease causes or increases the rates of cardiovascular diseases. In addition, current data do not indicate whether regular brushing and flossing or treatment of periodontal disease can cut the incidence of atherosclerosis, they noted.
"Recently, concern about possible links between periodontal disease (PD) and atherosclerotic vascular disease (ASVD) has intensified and is driving an active field of investigation into possible association and causality," wrote the committee, which comprises cardiologists, dentists, and infectious diseases specialists.
"The two disorders share several common risk factors, including cigarette smoking, age, and diabetes mellitus. Patients and providers are increasingly presented with claims that PD treatment strategies offer ASVD protection."
For more than a century, doctors have proposed that periodontal disease leads to systemic problems such as heart disease. But statements that imply a cause-and-effect relationship between periodontal disease and cardiovascular disease or that claim that dental treatment may prevent heart attack or stroke are "unwarranted" at this time, the statement authors said.
— Pam McClain, DDS, AAP president
"Although many ... studies have suggested positive associations between these two diseases, others have not, particularly after adjustment for potential confounding variables," the authors wrote.
Whether an independent, clinically significant association exists between the two disorders remains "controversial," they added.
"There's a lot of confusion out there," said Peter Lockhart, DDS, co-author and professor and chair of oral medicine at the Carolinas Medical Center. "The message sent out by some in healthcare professions that heart attack and stroke are directly linked to gum disease can distort the facts, alarm patients, and perhaps shift the focus on prevention away from well-known risk factors for these diseases."
Association, not causality
The AHA committee members conducted a literature search from May 2008 to July 2011 in Ovid MEDLINE on the association between PD and any cerebrovascular, peripheral vascular, or cardiovascular disease. The search covered the period of 1950 to July 2011 and included clinical studies, systematic reviews, and animal studies. A total of 537 peer-reviewed publications met the inclusion criteria.
After analyzing and comparing the findings of these studies, the committee concluded that observational studies to date support an association between PD and ASVD independent of known confounders. Because this information comes mostly from observational studies, however, "it does not demonstrate that PD is a cause of ASVD, nor does it confirm that therapeutic periodontal interventions prevent heart disease or stroke or modify the clinical course of ASVD," they wrote.
In addition, while the data indicate a general trend toward a periodontal treatment-induced suppression of systemic inflammation and improvement of noninvasive markers of ASVD and endothelial function, "the effects of PD therapy on specific inflammatory markers are not consistent across studies," the authors wrote.
For example, PD and ASVD both produce markers of inflammation such as C-reactive protein, and share other common risk factors, as well, including cigarette smoking, age, and diabetes mellitus, which may help to explain why diseases of the blood vessels and mouth occur in tandem, according to the authors.
Although several studies appeared to show a stronger relationship between these diseases, in those studies researchers didn't account for the risk factors common to both diseases, they noted.
"Much of the literature is conflicting," Dr. Lockhart said, "but if there was a strong causative link, we would likely know that by now."
The ADA’s Council on Scientific Affairs appointed a representative to the AHA expert committee that developed the report. The ADA Council on Scientific Affairs then reviewed the report and agreed with its conclusions.
"Although there is a body of research showing that gum disease is associated with several health conditions such as heart disease, stroke, and diabetes, just because two conditions are associated with each other does not mean that one causes the other," the ADA noted in a press release.
Long-term studies needed
While several short-term studies have shown that periodontal interventions result in a reduction in systemic inflammation and endothelial dysfunction, a large, long-term study would be needed to prove if dental disease causes heart disease and stroke, according to Dr. Lockhart. However, such a study isn't likely to be done in the near future, and it's most important to let patients know "what we know now, and what we don't know," he said.
Robert Genco, DDS, PhD, a distinguished professor of oral biology and microbiology at the University at Buffalo in New York who has spent years examining the link between periodontal disease and systemic diseases, said that while he doesn't disagree with the AHA statement, "it is not completely unrealistic to expect an association between PD and heart disease because of inflammation."
He contends that while causality is difficult to prove, the biological plausibility in this case -- inflammation -- is well-documented.
"We haven't looked at whether periodontal treatment can prevent someone from dying of a heart attack as end point," he told DrBicuspid.com. "But we have looked at surrogates, such as reducing inflammation, and there is some correlation."
Pam McClain, DDS, president of the American Academy of Periodontology (AAP), agreed.
"The conclusions of this literature review are not really any different than most other reviews," she told DrBicuspid.com. "The question is, does the evidence support an association between PD and ASVD? And in fact, it does."
“Periodontal disease and cardiovascular disease are both complex, multi-factorial diseases that develop over time. It may be overly simplistic to expect a direct causal link," Dr. McClain added. "The relationship between the diseases is more likely to be mediated by numerous other factors, mechanisms, and circumstances that we have yet to uncover. However, as the AHA statement points out, the association is real and independent of shared risk factors."
She pointed to a 2009 consensus report from the editors of the Journal of Periodontology (July 2009, Vol. 80:7, pp. 1021-1032) and The American Journal of Cardiology, which concluded that while a direct causal relationship between periodontitis and atherosclerotic cardiovascular disease has not been established, multiple studies do support two biologically plausible mechanisms:
- Moderate to severe periodontitis increases the level of systemic inflammation, a characteristic of all chronic inflammatory diseases, and periodontitis has been associated with increased systemic inflammation as measured by hsCRP and other biomarkers. Treatment of moderate to severe periodontitis sufficient to reduce clinical signs of the disease decreases the level of systemic inflammatory mediators.
- In untreated periodontitis, certain gram-negative bacteria may be found in periodontal pockets surrounding each diseased tooth and in approximation to ulcerated epithelium, and bacterial species found predominantly in the periodontal pockets also have been found in atheroma.
Thus, while the findings of the AHA committee do not support a causative relationship between PD and ASVD, Dr. McClain concluded, "studies have shown that if you reduce the body's inflammatory burden, you reduce the risk of heart attack."