To Örebro University

BACKGROUND AND AIMS: Individuals with inflammatory bowel disease (IBD) are at increased risk of serious infections, but whether this risk varies by histological disease activity is unclear.

METHODS: A national population-based study of 55,626 individuals diagnosed with IBD in 1990-2016 with longitudinal data on ileo-colorectal biopsies followed through 2016. Serious infections were defined as having an inpatient infectious disease diagnosis in the Swedish National Patient Register. We used Cox regression to estimate hazard ratios (HRs) for serious infections in the 12 months following documentation of histologic inflammation (vs. histological remission), adjusting for social and demographic factors, chronic comorbidities, prior IBD-related surgery and hospitalization. We also adjusted for IBD-related medications in sensitivity analyses.

RESULTS: With histological inflammation vs. remission, there was 4.62 (95%CI=4.46-4.78) and 2.53 (95%CI=2.36-2.70) serious infections per 100 person-years of follow-up, respectively (adjusted [a]HR=1.59; 95%CI=1.48-1.72). Histological inflammation (vs. remission) were associated with an increased risk of serious infections in ulcerative colitis (UC, aHR=1.68; 95%CI=1.51-1.87) and Crohn's disease (CD, aHR=1.59; 95%CI=1.40-1.80). The aHRs of sepsis and opportunistic infections were 1.66 (95%CI=1.28-2.15) and 1.71 (95%CI=1.22-2.41), respectively. Overall, results were consistent across age groups, sex and education level and remained largely unchanged after adjustment for IBD-related medications (aHR=1.47; 95%CI=1.34-1.61).

CONCLUSION: Histological inflammation of IBD was an independent risk factor of serious infections, including sepsis, suggesting that achieving histological remission may reduce infections in IBD.