Microscopic colitis and risk of incident rheumatoid arthritis: A nationwide population-based matched cohort study

BackgroundMicroscopic colitis (MC) has been linked to several autoimmune conditions. Results from previous studies on the association with rheumatoid arthritis (RA) have been inconsistent.AimTo assess the risk of future RA in MC.MethodsWe conducted a nationwide matched cohort study in Sweden of 8179 patients with biopsy-verified MC (diagnosed in 2007-2017), 36,400 matched reference individuals and 8202 siblings without MC, with follow-up until 2021. Information on MC was obtained from all of Sweden's regional pathology registers (n = 28) through the ESPRESSO cohort. Data on incident RA were collected from the National Patient Register. Using Cox regression, we calculated adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs).ResultsDuring a median follow-up of 9.1 years (interquartile range = 6.7-11.7), 73 MC patients and 183 reference individuals from the general population were diagnosed with RA (99 vs. 55 events per 100,000 person-years), equivalent to one extra case of RA in 226 patients with MC followed for 10 years. These rates corresponded to an aHR of 1.83 (95% CI = 1.39-2.41). The aHR was highest during the first year of follow-up (2.31 [95% CI = 1.08-4.97]) and remained significantly elevated up to 5 years after MC diagnosis (aHR 2.16; 95% CI = 1.42-3.30). Compared to siblings, without MC, the aHR was 2.04 (95% CI = 1.18-3.56).ConclusionPatients with MC are at a nearly two-fold risk of developing RA compared to the general population. Knowledge of this increased risk may expedite evaluation for RA in patients with MC presenting with joint symptoms and/or arthralgia, thus preventing delay until RA diagnosis. During the study period, 0.9% of patients with MC and 0.5% of the matched reference individuals were diagnosed with RA. These rates are equivalent to one extra case of RA in 226 patients with MC followed for 10 years.image

Automated summary

A study found that there is an association between microscopic colitis (MC) and rheumatoid arthritis (RA), with MC patients being nearly twice as likely to develop RA compared to the general population. This study is important as it highlights the need for expedited evaluation for RA in MC patients presenting with joint symptoms and/or arthralgia, thus preventing delay in RA diagnosis.