The aim of this study was to examine the risk of new-onset inflammatory bowel disease (IBD) following bariatric surgery.
We conducted a nationwide population-based prospective cohort study of the entire Danish population 18 to 60 years of age alive and residing in Denmark from 1996 to 2018. Bariatric surgery was included as a time-dependent variable, and Cox proportional hazards regression models were used to estimate hazard ratios (HRs) of IBD. We used a model adjusting for age, sex, and birth cohort and a multifactor-adjusted model additionally including educational status and number of obesity-related comorbidities.
We followed 3,917,843 individuals, of which 15,347 had a bariatric surgery, for development of new-onset IBD. During 106,420 person-years following bariatric surgery, 100 IBD events occurred (incidence rate 0.940 / 1000 person years). During 55,553,785 person-years without bariatric surgery, 35,294 events of IBD occurred (incidence rate 0.635 / 1000 person-years). This corresponded to a multifactor-adjusted HR of 1.15 (95% CI, 0.94-1.40) for IBD. Multifactor-adjusted HRs of Crohn’s disease (CD) and ulcerative colitis (UC) were 1.85 (95% CI, 1.40-2.44) and 0.81 (95% CI, 0.61-1.08), respectively. Among women, the multifactor-adjusted HR for CD was 2.18 (95% CI, 1.64-2.90). When limiting the study population to individuals with a diagnosis of overweight/obesity, bariatric surgery remained associated with increased risk of CD, multifactor-adjusted HR 1.59 (95% CI, 1.18-2.13).
This nationwide cohort study shows that bariatric surgery is associated with increased risk of development of new-onset CD, but not of UC. The underlying mechanisms remain elusive.