Association of Waist Circumference with the Risk of Inflammatory Bowel Disease: a Nationwide Cohort Study of 10 Million Individuals in Korea.

Background And Aims: Metabolic syndrome may share the pathophysiology of adipose tissue dysregulation and inadequate immune response with inflammatory bowel disease [IBD]. We determined the association of abdominal obesity [AO] with the risk of developing IBD.

Methods: We conducted a nationwide population-based cohort study using the Korean National Health Insurance Services database. A total of 10 082 568 participants of the 2009 national health screening programme were enrolled. Newly diagnosed Crohn's disease [CD] and ulcerative colitis [UC] were identified using the International Classification of Diseases 10th Revision and specialized national codes for rare intractable diseases. Waist circumference [WC] was classified into six groups and compared with the reference values of 85.0-89.9 cm for men and 80.0-84.9 cm for women. AO was defined as a WC of ≥90 cm for men and ≥85 cm for women.

Results: During a median follow-up of 9.3 years, the incidence rates of CD and UC were 2.11 and 8.40 per 100 000 person-years, respectively. After adjustment for age, sex, lifestyle behaviours, income and body mass index [BMI], the increase in baseline WC was significantly associated with the risk of developing CD, but not UC, compared to the references. The risk of developing CD in subjects with AO increased significantly compared to those without AO [adjusted hazard ratio, 1.40; 95% confidence interval, 1.21-1.61], regardless of obesity based on BMI.

Conclusions: Individuals with AO bore an increased risk of developing CD proportional to WC, but not UC, suggesting that visceral adiposity is related to the pathophysiology of CD.