Previous research suggests that poor oral hygiene leads to bacteria in the blood, causing inflammation in the body. Inflammation increases the risks of atrial fibrillation (irregular heartbeat) and heart failure (the heart's ability to pump blood or relax and fill with blood is impaired). This study examined the connection between oral hygiene and occurrence of these two conditions.

The retrospective cohort study enrolled 161,286 participants of the Korean National Health Insurance System aged 40 to 79 with no history of atrial fibrillation or heart failure. Participants underwent a routine medical examination between 2003 and 2004. Information was collected on height, weight, laboratory tests, illnesses, lifestyle, oral health, and oral hygiene behaviours.

During a median follow-up of 10.5 years, 4,911 (3.0%) participants developed atrial fibrillation and 7,971 (4.9%) developed heart failure.

Tooth brushing three or more times a day was associated with a 10% lower risk of atrial fibrillation and a 12% lower risk of heart failure during 10.5-year follow up. The findings were independent of a number of factors including age, sex, socioeconomic status, regular exercise, alcohol consumption, body mass index, and comorbidities such as hypertension.

While the study did not investigate mechanisms, one possibility is that frequent tooth brushing reduces bacteria in the subgingival biofilm (bacteria living in the pocket between the teeth and gums), thereby preventing translocation to the bloodstream.