People who brush their teeth three times a day or more have an 8% lower risk of developing diabetes, a study reveals.
In contrast, the presence of dental disease is associated with a 9% increased risk and 15 or more missing teeth is linked to a 21% increased risk, according to the research published in Diabetologia.
The authors analysed data collected between 2003 and 2006 on 188,013 subjects from the National Health Insurance System-Health Screening Cohort (NHIS-HEALS) in Korea.
Oral hygiene behaviours (number of tooth brushings, a dental visit for any reason and professional dental cleaning) were collected as self-reported data from dental health check-ups. The number of missing teeth was ascertained by dentists during examination.
The study found 17.5% of the included subjects had periodontal disease. After a median follow-up of 10 years, diabetes developed in 16% of people.
Using computer modelling, and after adjusting for patient demographics, physical activity, alcohol consumption, smoking status, vascular risk factors and history of cancer, the presence of periodontal disease and number or missing teeth were both linked to increased risk of developing diabetes by 9% and 21% respectively.
Frequent tooth brushing was associated with an 8% decreased risk of developing diabetes.
Further analysis revealed different results for adults aged 51 years and under compared to those 52 years and older.
For the younger group, brushing teeth twice a day was linked to a reduced risk of developing diabetes by 10% and three times by 14%, compared with those who brushed once a day or not at all.
In the older group, there were was no difference in diabetes risk between those brushing twice a day and those brushing once a day or not at all, however brushing three or more times per day compared with once or not at all was associated with a 7% decreased risk.
Periodontal disease appeared to have a stronger effect in younger adults: in the younger group it was associated with a 14% increased risk of diabetes, while in the older group the increased risk was 6%.
There were also differences between men and women, with stronger associations between increasing brushing and reduced diabetes risk in women.
The authors said that while the study does not reveal the exact mechanism connecting oral hygiene to development of diabetes, tooth decay, especially as it worsens, can contribute to chronic and systemic inflammation, and increase the production and circulation of inflammatory biomarkers.
Previous studies have shown inflammatory biomarkers are linked to insulin resistance and development of diabetes.
“Overall, improving oral hygiene may be associated with a decreased risk of occurrence of new-onset diabetes,” the authors said.