Older adults who have higher proportions of four periodontal-disease–causing bacteria in their mouths also tend to have thicker carotid arteries, according to a study in the Feb. 8 issue of the American Heart Association journal Circulation.
"Although more than 600 bacteria have been shown to colonize the mouth, each person tends to carry different proportions of these microbes," said co-author Dr. Panos N. Papapanou, professor and chair, Section of Oral and Diagnostics Sciences, and the director, Division of Periodontics, Columbia University School of Dental and Oral Surgery. He noted that only a subset of bacteria tends to be dominant in dental plaque.
"We wanted to know whether it was true that the greater the proportion of so-called ‘bad’ bacteria in the mouth, the higher the likelihood of a thickened carotid artery," added Dr. Papapanou.
To find an answer, researchers, led by Moïse Desvarieux, M.D., Ph.D., an infectious disease epidemiologist, Columbia University’s Mailman School of Public Health and the University of Minnesota, collected on average seven dental plaque samples from each of 657 older adults who had not lost their teeth and were enrolled in Oral Infections and Vascular Disease Epidemiology Study, a multidisciplinary endeavor sponsored by the National Institute of Dental and Craniofacial Research. Researchers took diseased and healthy samples from predetermined sites in the mouth and evaluated them for 11 oral bacteria, including four widely regarded to be involved in causing periodontal disease: Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola. The other seven bacteria served as controls, as their roles in periodontal disease were neutral or had not been established yet.
Subjects underwent carotid intima-media thickness (IMT) measurement to evaluate their cardiovascular health. They also each provided a blood sample to determine their C-reactive protein levels; C-reactive protein has been reported to be elevated in people with periodontal disease, and studies have found that testing for this protein may help predict the development of heart disease.
Controlling for several risk factors that might skew their data—such as smoking and diabetes—researchers found the higher the levels of these periodontal-disease–causing bacteria, the more likely subjects were to have thicker carotid arteries. Researchers noted no association between IMT, the periodontal pathogens and C-reactive protein levels, which suggests that the protein is involved in another cardiovascular disease pathway.
Next, researchers wondered whether the broad association might be due to the four pathogens involved in causing periodontal disease, which, when combined, accounted for only 23 percent of the bacteria in dental plaque. If so, the finding would provide added specificity to strengthen the case for the association.
"After reanalyzing the data, we found, with the exception of an oral bacterium called Micromonas micros, the relationship was limited to these four established oral pathogens," said co-author David Jacobs, Ph.D., a professor in the Division of Epidemiology at the University of Minnesota School of Public Health.
"It now becomes crucial to follow the participants over time and see whether these baseline findings hold up and further translate into clinical disease," continued Dr. Jacobs.
