Minimal Increase in RA Risk from Periodontitis, Raises Questions on Bidirectional Effects in new study

These findings, published in ACR Open Rheumatology, question the previously established bidirectional connections between periodontitis and RA, highlighting residual confounding as a significant factor and prompting a reevaluation of the biological plausibility and clinical relevance of these associations.

Results from an analysis of about 2.6 million Danes, followed from 2000 to 2017, suggested that "periodontitis may slightly, but practically negligibly, raise the risk of incident RA, whereas RA did not increase the risk of incident periodontitis.

"After adjusting for sex, age, dental service use, and country of birth, the residual cross-sectional association between these conditions was completely explainable by the confounding of smoking," the researchers wrote.

Periodontitis, a common inflammatory condition affecting the gums and supporting structures of the teeth, has previously been associated with an increased risk of various systemic diseases, including cardiovascular diseases and diabetes. Similarly, rheumatoid arthritis, an autoimmune disorder characterized by joint inflammation, has been hypothesized to share common pathways with periodontitis due to its inflammatory nature.

Against the above background, Eero Raittio, Aarhus University, Aarhus, Denmark, and colleagues investigated the bidirectional relationship between RA and periodontitis and their cross-sectional association using national administrative health care data.

The sample comprised 3,308,903 individuals 20 to 79 years of age who resided in Denmark in 2000 and had remained free of RA and periodontitis in the last ten years. Periodontitis and RA were defined using diagnosis and treatment codes. Marginal structural survival models were utilized to assess the impacts of RA on the incidence of periodontitis and vice versa from 2000 to 2017.

Using a cross-sectional sample of 2,574,536 individuals from 2017, the association of periodontitis with RA was investigated, simulating RA and periodontitis misclassification and unmeasured confounding of smoking.

The study revealed the following findings:

• Between 2000 and 2017, 20,348 individuals developed RA, and 740,799 developed periodontitis.
• The estimated hazard ratio (HR) for the effect of periodontitis on incident RA was 1.05, resulting in a restricted mean survival time difference of one day.
• The HR for the effect of RA on incident periodontitis was 0.84, corresponding to a restricted mean survival time difference of 151 days.
• Cross-sectionally, the unadjusted prevalence ratio for the association was 1.15, whereas the estimate adjusted for measured and simulated confounding was practically null (0.99).

The findings showed that periodontitis may slightly, but practically negligibly, raise the risk of incident RA, whereas RA did not increase the risk of incident periodontitis. Additionally, after age, sex, country of birth, and dental service use adjustments, the residual cross-sectional association between these conditions was completely explainable by the confounding of smoking.

"These findings question the previously documented bidirectional influences between periodontitis and RA, highlighting residual confounding as a pivotal linking factor. This prompts a reassessment of the biological plausibility and clinical significance of these associations," the researchers concluded.

Reference:

Raittio, E., Nascimento, G. G., Lopez, R., & Baelum, V. Exploring the Bidirectional Relationship Between Periodontitis and Rheumatoid Arthritis in a Large Danish Cohort. ACR Open Rheumatology. https://doi.org/10.1002/acr2.11718