A review of published research worldwide showed increasing incidence of both Crohn disease and ulcerative colitis but lacked data from developing countries.

To summarize worldwide data on the incidence and prevalence of inflammatory bowel disease (IBD) — which comprises ulcerative colitis (UC) and Crohn disease (CD) — researchers systematically reviewed 238 incidence and 122 prevalence studies. The highest percentage of studies came from Europe, the second highest from Asia and the Middle East, and the third highest from North America.