Increased prevalence of autoimmune diseases in functional gastrointestinal disorders: case-control study of 23 471 primary care patients

Background: There is increasing evidence that impaired mucosal defence mechanisms are implicated in the pathogenesis of the functional gastrointestinal disorders (FGIDs), allowing inappropriate immune activation. Aim: To test the hypothesis that an excess of autoimmune disorders among sufferers, using a large primary care database to examine this. Methods: Cases were diagnosed with FGIDs – irritable bowel syndrome (IBS), functional dyspepsia (FD), chronic idiopathic constipation (CIC), and multiple FGIDs. Controls were those without FGIDs. Prevalence of autoimmune disorders was compared between cases and controls using odds ratios (ORs) and 95% confidence intervals (CIs). Results: We included 23 471 patients (mean age 51.4 years, 66.1% female). Prevalence of autoimmune disorders was greater among all FGIDs, compared with controls without. In those with FD (OR 1.35; 95% CI 1.12–1.63), CIC (OR 1.75; 95% CI 1.11–2.75), or multiple FGIDs (OR 1.49; 95% CI 1.25–1.77) this was statistically significant after controlling for age and gender. Rheumatological autoimmune disorders were significantly more frequent in those with FD (OR 1.44; 95% CI 1.15–1.80), CIC (OR 1.84; 95% CI 1.08–3.13), or multiple FGIDs (OR 1.53; 95% CI 1.24–1.88), after controlling for age and gender. However, endocrine autoimmune disorders were no more frequent in those with FGIDs, after controlling for age and gender. Conclusions: In a large sample of primary care patients, there was a significantly higher prevalence of autoimmune disorders among those with FD, CIC, or multiple FGIDs not explained by differences in age or gender. We were unable to control for concomitant drug use, which may partly explain this association