Poorer oral hygiene — while not recommended — was linked to a lower risk of inflammatory bowel diseases (IBD) in a study developed by researchers at the Karolinska Institutet and Örebro University Hospital in Sweden.
Their prospective cohort study, “Inverse Association Between Poor Oral Health and Inflammatory Bowel Diseases,” was published in the journal Clinical Gastroenterology and Hepatology.
What is known as the “hygiene hypothesis” states that a lack of childhood exposure to microorganisms, due to improved hygienic conditions, modulates the development of the immune system, predisposing it to autoimmune diseases. This hypothesis has been suggested as a reason for the increased incidence of IBD, such as Crohn’s disease and ulcerative colitis, now witnessed.
Previous studies into oral hygiene and IBD development have produced inconsistent results, and the issue is of considerable debate. The researchers conducted a prospective cohort study to evaluated the oral hygiene of 20,162 people, focusing on tooth loss, dental plaques, and oral mucosal lesions at enrollment. Participants were followed for 40 years, and those who later developed IBD were identified.
The team reported that during follow-up, 142 participants developed Crohn’s disease and 67 developed ulcerative colitis, accounting for an overall incidence of IBD of 37.3 per 100,000 person-years.
Results, indeed, revealed that those with poor oral health were better protected from IBD. In fact, those that reported the loss of five to six teeth, out of the six Ramfjord index teeth at baseline (a measure of periodontal disease), had a 44 percent reduced risk of developing IBD. Similarly, participants who had dental plaques covering more than a third of the tooth surface had a 68 percent reduced risk of Crohn’s disease, but not ulcerative colitis. Lesions in the oral mucosa at baseline also seemed to be protective against IBD, but this association was not statistically significant.
“Our data on a negative relationship between poor oral health and later IBD supports the ‘hygiene hypothesis,’” the researchers concluded. “We believe that excessive oral hygiene might generate dysbiosis in bacterial colonization, dysregulate the innate immune responses and promote the inflammatory process. Conversely, poor oral health might contribute to the induction of immune tolerance and suppression of overreactive inflammation, thereby reducing the risk of immune-mediated diseases such as IBD.”
The researchers warn, however, that these findings should not encourage a lack of oral hygiene, but instead suggest that over-protective daily hygiene should be avoided.