New research finds that brushing the teeth three or more times a day significantly reduces the risk of atrial fibrillation and heart failure.

The bacteria in our mouths may hold the key to many facets of our health.

Researchers have found intriguing clues about pancreatic and esophageal cancer risk in mouth bacteria, and some studies have linked poor oral hygiene with respiratory problems.

Mounting evidence is also strengthening the link between oral health and cardiovascular health.

For instance, some studies have found oral bacteria in the blood clots of people receiving emergency treatment for stroke, and experts have linked severe gum disease with a significantly higher risk of hypertension.

Conversely, destroying "friendly" oral bacteria that help maintain a healthy and balanced oral microbiome could disrupt blood pressure levels and also lead to hypertension.

Maintaining good oral health, therefore, seems to be key to cardiovascular health.

Now, a new study that appears in the European Journal of Preventive Cardiology suggests that regular toothbrushing may keep heart failure and atrial fibrillation (A-fib) — a type of arrhythmia — at bay.

Dr. Tae-Jin Song of Ewha Womans University in Seoul, Korea, is the senior author of the new study.

In their paper, Dr. Song and team explain that the motivation for the study hinges on the mediating role of inflammation. They write, "Poor oral hygiene can provoke transient bacteremia and systemic inflammation, a mediator of atrial fibrillation and heart failure."

Studying A-fib, heart failure, and oral hygiene

In their study, Dr. Song and team examined atrial fibrillation's associations with both heart failure and poor oral hygiene. They used data from 161,286 people who were part of the Korean National Health Insurance System-Health Screening Cohort.

A-fib is a condition affecting at least 2.7 million people in the United States. In people with A-fib, the heart cannot efficiently pump blood to the rest of the body because it does not beat regularly.

The heart also does not pump blood as it should in people with heart failure. This inefficiency results in fatigue and, sometimes, breathing difficulties, as insufficient oxygen reaches the other organs in the body.

The participants of the current study were 40–79 years old and had no history of either A-fib or heart failure. During enrollment, which took place between 2003 and 2004, the team measured the height and weight of each of the participants and asked them questions about their lifestyle, oral health, and oral hygiene habits.

The participants also underwent some laboratory tests, which included blood tests, urine tests, and blood pressure readings.

Brushing lowers heart failure risk by 12%

Over a median follow-up period of 10.5 years, 4,911 participants received a diagnosis of A-fib, and 7,971 developed heart failure.

Brushing the teeth three times or more a day was linked with a 10% lower chance of developing A-fib and a 12% lower risk of heart failure.

Confounding factors — including age, sex, socioeconomic status, physical activity, alcohol intake, body mass index, and other coexisting conditions, such as hypertension — did not influence these results, as the researchers accounted for them in their analysis.

The authors conclude:

"Improved oral hygiene care was associated with decreased risk of atrial fibrillation and heart failure. Healthier oral hygiene by frequent toothbrushing and professional dental cleanings may reduce risk of atrial fibrillation and heart failure."

However, they also note that, as with any observational study, the research is limited and cannot explain causation. The study is also limited because it only looked at people living in one country, so the results may not be generalizable.

Nonetheless, notes the study's senior author, "We studied a large group over a long period, which adds strength to our findings."

Study strengths and limitations

In an accompanying editorial, authors Pascal Meyre, from the Cardiovascular Research Institute at the Basel University Hospital in Switzerland, and David Conen, from the Population Health Research Institute, McMaster University, Canada, offer a critical look at the findings.

They agree that the strengths of the study "are the large sample size, with over 160,000 individuals included in the study, the large number of outcome events, and the long follow-up duration."

"This allowed the investigators to carry out meaningful analyses and adjust the multivariable models for many covariates, such that some of the confounding could be controlled," they add.

However, the retrospective design of the study "may have introduced selection bias," say the authors of the editorial. Furthermore, the participants' "level of education, marital status, and information on inflammatory biomarkers, such as C-reactive protein, were not available."

The information on toothbrushing and oral hygiene habits was self-reported, which might subject it to recall bias, write Meyre and Conen.

"The causality of these associations is unclear, and it is certainly too early to recommend toothbrushing for the prevention of [A-fib] and [congestive heart failure]," they conclude:

"While the role of inflammation in the occurrence of cardiovascular disease is becoming more and more evident, intervention studies are needed to define strategies of public health importance."