Study Identifies Association Between Microscopic Colitis and RA Diagnosis

Results of recent data presented at Digestive Disease Week (DDW) 2023 revealed that patients with microscopic colitis (MC) were almost twice as likely to be diagnosed with rheumatoid arthritis (RA) when compared with the general population.¹

“Few studies have investigated the association between MC and RA and findings are inconsistent, ranging from a positive to no association,” wrote David Bergman, MD, Karolinska Institutet Institutionen for medicinsk epidemiologi och biostatistik in Stockholm, Sweden, and colleagues. “As arthralgia and immune-mediated disorders are common in patients with MC, we aimed to elucidate the association between MC and future RA using a large population-based cohort.”

Swedish patients with a colonic biopsy consistent with MC between 2004 and 2017 were identified through the nationwide ESPRESSO cohort study. Each patient with MC were then matched with up to 5 controls from the general population according to age, sex, county of residence, and index date. RA data were collected from the Swedish Patient Register. Those with a previous diagnosis of RA or other rheumatic conditions including juvenile idiopathic arthritis (JIA), polyarthritis, psoriatic arthritis (PsA), and spondyloarthritis were excluded from the study.

A Cox proportional hazards mode was used to determine the point estimate for the relation between MC and RA. Further, the potential impact of reverse causality was evaluated using a sensitivity analysis in which study participants with a RA diagnosis during the first year of follow-up were excluded from the analysis.

Investigators identified 11,293 patients with a first-time MC diagnosis, which were then matched to 52,213 reference patients from the general population. During the median follow-up period of 8 years (interquartile range [IQR] = 5.4-11.1), a total of 129 (1.1%) of patients with MC and 317 (.6%) of patients in the control cohort were diagnosed with RA. These figures corresponded to incidence rates (IRs) of RA of 143 per 100,000 person-years years (95% confidence interval [CI] = 120-170) for MC and 74 per 100,000 person-years (95% CI = 66-82) for the reference controls.

After investigators adjusted for the matching variables, the Cox proportional hazards model demonstrated an adjusted hazard ratio (HR) of 1.92 (95% CI = 1.56-2.34) for individuals with MC compared to the general population group. Excluding the first year of follow-up was not proven to materially change the point estimate (aHR =1.80 [95% CI =1.44-2.25]).

“This finding highlights the need for clinicians to consider RA in MC patients presenting with arthralgia or other joint symptoms,” investigators concluded.

References

1. ^{Bergman D, Khalili H, Ebrahimi F, Sun J, et al. MICROSCOPIC COLITIS AND FUTURE RISK OF RHEUMATOID ARTHRITIS: A NATIONWIDE MATCHED COHORT STUDY.Abstract presented at Digestive Disease Week (DDW) 2023 Annual Meeting. Chicago, IL. May 6-10, 2023.}