Epidemiology of UC
Prevalence of UC
IBD is a prevalent condition in the United States, affecting approximately 1 million people. It is believed to be almost twice as common in Northern Europe, with a prevalence of 2 million people. With regard to the spectrum of disease, UC appears to occur more frequently than Crohn's. Estimates suggest that the prevalence of UC among individuals in the US is 100-200 cases per 100,000 people.
Whether the incidence and prevalence of IBD is increasing has been an active area of research. Prior to 1940, UC was more common than Crohn's disease in the US. After 1940, an increase in the incidence of Crohn's disease was noted. Between 1940 and 1990, a rise in the US prevalence of both disorders was described. Since the early 1990's, reports suggest that the incidence of UC and Crohn's has plateaued and there may be a decrease in disease prevalence in some areas of the US. There have been discrepancies among studies, however, depending on location, age of population, and methodologies.
Age Distribution of UC
While IBD can be diagnosed at any age, two peaks of disease onset are most commonly seen: 1) between 15-30 years and 2) around age 50 years. Approximately 25% of patients with IBD develop disease during childhood and adolescence. Recent studies have suggested that among young children with IBD (<5years), the incidence of UC is greater than Crohn's. Over time, there is a reversal of this trend with a higher incidence of Crohn's disease in adolescence than UC.
Gender Distribution of UC
UC affects males and females at equivalent rates.
Geographic Distribution of UC
The highest prevalence of IBD is seen in so-called "developed" and "Westernized" regions of the world such as the US and Northern Europe. There have been several reports, however, of increasing incidence in Asia. One interesting trend that has been observed is an apparent north-south disease gradient. Investigators have described higher incidence rates in northern latitudes which decrease across southern latitudes. The rationale for this is not well understood but may be related to pathogens residing in these latitudes or population genetics.
Racial/Ethnic Distribution of UC
IBD is most common in the Caucasian population with a higher predilection among those of Jewish descent. Within the US, increasing disease incidence has been noted among African Americans and Hispanics. Whether this change in disease pattern is due to environment or improvements in diagnosis and access to care remains speculative.