Association between antibiotics use and the risk of rheumatoid arthritis: a retrospective cohort study in South Korea.

Objectives: Certain studies propose that antibiotic use may influence rheumatoid arthritis (RA) incidence, but the clear association between antibiotics and RA remains unclear. Therefore, this study aimed to examine the relationship between antibiotics and RA risk to provide additional epidemiological evidence.
Methods: This population-based retrospective cohort study was conducted with adults aged 40 years or older using the Korean National Health Insurance Service (NHIS) database. Antibiotic exposure was measured from 2003 to 2007. Study participants were followed up from January 1, 2008, to December 31, 2019. Multivariable Cox hazard regression was utilized to evaluate adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) for the risk of RA according to accumulative days of antibiotic use and the number of antibiotic classes used, respectively.
Results: During 3,395 590 person-years of follow-up, 29 274 cases of RA were identified. Participants who used antibiotics for 91 or more days had a higher risk of RA (aHR, 1.79; 95% CI, 1.67-1.92) than antibiotic non-users. Additionally, individuals who used four or more kinds of antibiotic classes had a higher risk of RA (aHR, 1.61; 95% CI, 1.51-1.71) than those who did not prescribe antibiotics. The risk of RA was positively associated with both higher cumulative days of antibiotic exposure and a larger number of drug classes. These trends were maintained in sensitivity analyses, including variations in antibiotic exposure periods.
Conclusion: Our findings suggest a possible association between the long-term use of antibiotics and RA incidence. Further studies are necessary for a clearer understanding of this association.
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