Abstract and Introduction
Abstract
Background & Aims: We conducted a systematic review to determine changes in the worldwide incidence and prevalence of ulcerative colitis (UC) and Crohn's disease (CD) in different regions and with time.
Methods: We performed a systematic literature search of MEDLINE (1950–2010; 8103 citations) and EMBASE (1980–2010; 4975 citations) to identify studies that were population based, included data that could be used to calculate incidence and prevalence, and reported separate data on UC and/or CD in full manuscripts (n = 260). We evaluated data from 167 studies from Europe (1930–2008), 52 studies from Asia and the Middle East (1950–2008), and 27 studies from North America (1920–2004). Maps were used to present worldwide differences in the incidence and prevalence of inflammatory bowel diseases (IBDs); time trends were determined using joinpoint regression.
Results: The highest annual incidence of UC was 24.3 per 100,000 person-years in Europe, 6.3 per 100,000 person-years in Asia and the Middle East, and 19.2 per 100,000 person-years in North America. The highest annual incidence of CD was 12.7 per 100,000 person-years in Europe, 5.0 person-years in Asia and the Middle East, and 20.2 per 100,000 person-years in North America. The highest reported prevalence values for IBD were in Europe (UC, 505 per 100,000 persons; CD, 322 per 100,000 persons) and North America (UC, 249 per 100,000 persons; CD, 319 per 100,000 persons). In time-trend analyses, 75% of CD studies and 60% of UC studies had an increasing incidence of statistical significance (P < .05).
Conclusions: Although there are few epidemiologic data from developing countries, the incidence and prevalence of IBD are increasing with time and in different regions around the world, indicating its emergence as a global disease.
Introduction
The inflammatory bowel diseases (IBDs), consisting of ulcerative colitis (UC) and Crohn's disease (CD), are characterized by chronic inflammation of the gastrointestinal tract in genetically susceptible individuals exposed to environmental risk factors. The etiology of IBD has been extensively studied in the past few decades; however, disease pathogenesis is not fully understood. Considerable variation in the epidemiology of IBD has been observed around the world, with a wide range of estimates both within and between geographic regions. IBD is believed to be associated with industrialization of nations, with the highest incidence rates and prevalence of IBD in North America and Europe. The incidence of IBD may be rising in developing nations as they have become industrialized. However, population-based epidemiologic data of IBD collected in a standardized fashion in developing nations are sparse. Several studies have reported that the incidence of IBD has increased markedly over the latter part of the 20th century, while other studies have suggested a plateau or even decline in incidence in certain geographic regions.
To properly interpret the incidence or prevalence data and evaluate time trends, a systematic review of all population-based studies that describes the incidence and/or prevalence of IBD is needed. Insight into the worldwide epidemiology of IBD is important for the identification of geographic patterns and time trends. This information may help researchers study environmental risk factors of IBD, describe the burden of IBD, assist with international health resource utilization planning, and direct research initiatives in countries lacking incidence data on IBD. The objectives of our study were to conduct a systematic review of the worldwide incidence and prevalence of UC and CD and to evaluate the change in incidence across different geographic regions and time periods.