An analysis of data on oral bacteria and hypertension from more than 1,200 postmenopausal women revealed that 10 types of bacteria were associated with a 10% to 16% higher risk of developing high blood pressure. Meanwhile, five other bacterial species were associated with a 9% to 18% lower hypertension risk, researchers report in the Journal of the American Heart Association.
"We're starting to have more and more evidence that oral health is related to overall systemic health, and blood pressure in this instance is an indication of that," said first author Dr. Michael LaMonte of the School of Public Health at the University of Buffalo, New York. "We all have a mixture of bacteria in our mouths at any given time, both above the gums, teeth and tongue and those that are below the gums."
"In those with healthier mouths - people with no swollen gums, no lost teeth and no gingivitis - there is a balance between good and bad bacteria. There is evidence that in those with swollen, bleeding gums and those that have separated from the tooth roots, the balance between the two shifts to the bad bacteria."
To explore whether oral bacteria could be associated with increases in blood pressure, Dr. LaMonte and his team turned to the Buffalo Osteoporosis and Periodontal Disease (OsteoPerio) study, which is ancillary to the Women's Health Initiative Observational study (WHIOS).
In their analysis, the researchers included 1,215 women who were aged 53 to 81 at enrollment in the OsteoPerio study. The participants had provided medical and lifestyle histories and completed a baseline oral examination during which subgingival plaque samples were collected.
At the outset, 429 women had a healthy blood pressure (readings below 120/80 mm Hg), without help from medication, while 306 had elevated blood pressure but were not taking medication. Among these 735 women who were not being treated for hypertension, 375 were newly diagnosed with hypertension during the 10.4 years of follow-up.
In a cross-sectional analysis, the researchers found 47 bacterial species out of a total of 245 that differed significantly by baseline BP status.
On prospective analysis, 15 bacterial species at baseline were significantly associated with incident hypertension, 10 positively and five inversely. The findings were similar after adjustment for confounders, but were no longer significant after adjusting for multiple comparisons.
Dr. LaMonte has two proposals that might help explain the findings. "Certain bacteria in the mouth have the ability to convert nitrates in certain foods to nitrites, which ultimately leads to a very important source of chemical blood pressure regulation: nitric oxide."
Without the right balance of oral bacteria, "humans have a very challenging time converting dietary intake into nitric oxide," Dr. LaMonte said.
The other way these oral bacteria might be leading to increases in blood pressure is by escaping the mouth. "When the gums become inflamed, their blood vessels become leaky," the researcher explained. "The bacteria can get out of the oral cavity and circulate around the body and go to places you don't want them to go. One of those places is the artery walls where plaques is starting to form."
In earlier research, Dr. LaMonte and his team proved this was possible. "We took samples of plaques out of people's arteries," he said. "When we tested them we found periodontal bacteria, which are found nowhere else in the body."
The new study is "interesting," said Dr. Emeran Mayer, a research professor of medicine at the University of California, Los Angeles, and founding director of the UCLA Microbiome Center.
But ultimately, it's an observational study and not a randomized controlled trial, so you can't be sure how, or if, the oral microbiome is implicated in the development of hypertension in menopausal women, Dr. Mayer said.
It also has the limitation of "all these current microbiome papers," Dr. Mayer said. "It's based on individual organisms and not on their functions."
Still, Dr. Mayer said, the study may spark more research and even a randomized clinical trial.
SOURCE: https://bit.ly/34aEQu7 Journal of the American Heart Association, online March 2, 2022.
By Linda Carroll
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