Association Between Rheumatoid Arthritis and Gastrointestinal Comorbidities: Evidence From Taiwan's National Health Insurance Database.

[BACKGROUND] Rheumatoid arthritis (RA) is a systemic autoimmune disease with known extra-articular manifestations, including potential involvement of the gastrointestinal (GI) tract. While prior studies have explored malignancy risks in RA, limited large-scale data exist on the association between RA and both cancerous and non-cancerous GI comorbidities.

[METHODS] This retrospective nested case-control study utilized Taiwan's National Health Insurance Research Database (NHIRD) from 2000 to 2019. A total of 75 670 individuals newly diagnosed with RA were matched 1:4 by age and sex to 302 680 controls without RA. The prevalence and adjusted odds ratios (aOR) for GI conditions-including gastric ulcer, duodenal ulcer, GERD, irritable bowel syndrome, inflammatory bowel diseases, and various GI cancers-were evaluated using conditional logistic regression.

[RESULTS] Patients with RA demonstrated significantly higher odds of several benign GI conditions, including peptic ulcer disease (aOR: 1.72, 95% CI: 1.66-1.79), gastric ulcer (aOR: 1.52, 95% CI: 1.44-1.60), GERD (aOR: 1.49, 95% CI: 1.41-1.57), and inflammatory bowel diseases. These associations remained robust across age- and sex-stratified analyses. In contrast, most GI cancers were not significantly associated with RA. Notably, inverse associations were observed for stomach cancer (aOR: 0.66, 95% CI: 0.49-0.87) and liver and bile duct cancer in females (aOR: 0.74, 95% CI: 0.58-0.95).

[CONCLUSION] RA is significantly associated with a higher prevalence of benign GI comorbidities but not with most GI malignancies. These findings highlight the importance of comprehensive GI screening in RA management and support the relevance of the gut-joint axis in autoimmune disease pathogenesis.