BACKGROUND AND AIMS: The wide variation in inflammatory bowel disease (IBD) incidence across countries entails an opportunity to recognize global disease determinants and hypothesize preventive policies.
METHODS: We fitted multivariable models to identify putative environmental, nutritional and socio-economic determinants associated with the incidence of IBD [i.e. ulcerative colitis (UC) and Crohn's disease (CD)]. We utilized the latest available country-specific incidence rates, and aggregate data for 20 determinants, from over 50 countries accounting for more than half of the global population. We presented the associations with exponentiated beta coefficients [exp(β)] indicating the relative increase of disease incidence per unit increase in the predictor variables.
RESULTS: Country-specific incidence estimates demonstrate wide variability across the world, with a median of 4.8 new UC cases (IQR 2.4-9.3), and 3.5 new CD cases (IQR 0.8-5.7) per 100,000 population per year. Latitude [exp(β) 1.05, 95% CI 1.04‒1.06, per degree increase], prevalence of obesity (1.05, 1.02‒1.07, per 1% increase) and of tobacco smoking (0.97, 0.95‒0.99, per 1% increase) explained 71.5% of UC incidence variation across countries in the adjusted analysis. The model for CD included latitude (1.04, 1.02‒1.06), expenditure for health (1.03, 1.01‒1.05, per 100 PPP/year per capita increase) and physical inactivity prevalence (1.03, 1.00‒1.06, per 1% increase) explaining 58.3% of incidence variation across countries. Besides expenditure for health, these associations were consistent in low/middle- and high-income countries.
CONCLUSIONS: Our analysis highlights factors able to explain a substantial portion of incidence variation across countries. Further high-quality research is warranted to develop global strategies for IBD prevention.