What Can We Learn from Epidemiological Studies in Inflammatory Bowel Disease?

Population-based studies represent the whole spectrum of patient population and should represent the mainstay when evaluating patients' prognosis. A high number of CD patients need surgical intervention during the disease course. The disease course of inflammatory bowel diseases, including ulcerative colitis (UC) and Crohn's disease (CD), is quite varied and still quite unpredictable. Key Messages: According to earlier studies, up to 60% of patients undergo at least one operation after 10 years of CD duration. Newer cohorts report lower cumulative probability of surgery of approximately 40% after 10 years. The colectomy rate in UC is approximately 10% after 10 years from diagnosis with a geographic difference. Similarly to CD, the colectomy rate seems to decrease over time. There is some evidence that the increasing use of immunosuppressive and/or biological therapy might have been responsible for this favourable trend. However, other factors may have an impact on decreasing surgical trend over time. The relative risk (RR) of colorectal cancer (CRC) in UC is approximately doubled compared to background population. However, the absolute risk in general is relatively low between 1.1 and 5.3% after 20 years of disease duration. Furthermore, a decreasing trend in the incidence of CRC has been reported in recent studies. Importantly, several factors such as disease extent, activity, age at UC onset, and so on may increase/modify an individual risk. Similar to UC, CD patients have approximately 2 times higher RR of cancer compared to background population. The risk is higher for colon than for rectum cancer and present only in CD patients with colonic involvement.

The surgery rate in CD has decreased over the time period. The evidence on colectomy rate in UC is less conclusive. The RR of CRC in UC and CD is approximately doubled compared to that of the background population, but it seems to be decreasing in more recent cohorts.