Irritable Bowel Syndrome and Rheumatoid Arthritis: Prevalence, Epidemiological Characteristics and Associated Risk Factors

Introduction: Rheumatoid arthritis (RA) has been associated with several gastrointestinal (GI) manifestations, including gastrointestinal bleeding and rheumatoid vasculitis of the GI tract. RA has also been linked with irritable bowel syndrome (IBS). Methods: The national inpatient sample was used to study age, gender, race and associated co-morbidities in patients with RA (ICD9 714.0) and IBS (ICD9 564.1) in the year 2014. Multiple logistic regression by backward selection was used to analyze risk factors that were associated with RA and IBS. Results: Out of a total of 7,071,762 records, 110,343 or 1.5% of the population had a diagnosis of rheumatoid arthritis. 59,249 or 0.8% of the population had a diagnosis of irritable bowel syndrome. A total of 2,259 patients had a combination of RA and IBS. 2.0% of patients with RA had IBS and 3.8% of patients with IBS had RA. Slightly over half or 51% of the population was over the age of 65 years. 38.2% were in the age group of 44-65 years. Nearly all were female (90.2 %; p < 0.001) and Caucasian (86.5% p < 0.001). By logistic regression, female gender was strongly associated with RA & IBS (OR 6.9 95% CI 5.9 - 7.9 p< 0.001). Prevalence was also higher in the age group between 44-65 years (OR 22.4 95% CI 12.0-42.0 p< 0.001) followed by age group > 65 years (OR 14.9 95% CI 7.9 - 28.2 p< 0.001). Caucasian race had a higher association (OR 19.5 95% CI 10.0-38.0 p < 0.001).The prevalence was higher in the presence of other rheumatological diseases once adjusted for age, gender & race. Fibromyalgia was associated with IBS in RA patients (OR 9.5 95% CI 8.3 - 10.7 p< 0.001) as was psoriatic arthritis (OR 5.1 95% CI 3.3 - 7.8 p<0.001) and osteoarthritis (OR 1.9 95% CI 1.7 - 2.1 p<0.001). Other risk factors studied: smoking status, gout, hypertension, diabetes, chronic kidney disease, coronary artery disease, chronic obstructive pulmonary disease and heart failure had no significant effect. Conclusion: Alterations in the intestinal microbiota and inflammatory changes have been postulated for IBS. Chronic inflammatory disease like RA may thus predispose to its development. In our study, IBS affected 2.0% of patients with RA. Prevalence was higher in the female gender, ages 44 to 65 years and Caucasians. Presence of fibromyalgia, psoriatic arthritis and osteoarthritis conferred a higher risk of IBS. Further research is warranted to identify patients who might be at increased risk for IBS.