Increasing Incidence and Prevalence of the Inflammatory Bowel Diseases With Time, Based on Systematic Review

Natalie A. Molodecky; Ing Shian Soon; Doreen M. Rabi; William A. Ghali; Mollie Ferris; Greg Chernoff; Eric I. Benchimol; Remo Panaccione; Subrata Ghosh; Herman W. Barkema; Gilaad G. Kaplan

Disclosures

Gastroenterology. 2012;142(1):46-54. 

In This Article

Results

The search strategy retrieved 8444 unique citations; 8103 were identified from MEDLINE and 4975 from EMBASE. Of these, 7938 citations were excluded after the first screening based on titles and abstracts, leaving 506 articles for full text review (Figure 1). The observed agreement between reviewers for eligibility of articles on this first screening was 97%, corresponding to a κ statistic of 0.77. On full text review of 506 articles, 246 were excluded for the reasons listed in Figure 1, leaving 260 studies (238 incidence studies and 122 prevalence studies) for final inclusion in the systematic review. Of the 238 incidence studies, 185 investigated the incidence of CD and 161 investigated the incidence of UC. Of the 122 prevalence studies, 96 investigated the prevalence of CD and 79 investigated the prevalence of UC. The agreement between reviewers for eligibility of articles was 100%, corresponding to a κ of 1. Characteristics of the 238 included incidence studies and 122 prevalence studies, including references, are shown in Appendix 2 and Appendix 3 , respectively. The incidence studies were conducted in different geographic regions, with 159 studies from Europe, 41 studies from Asia and the Middle East, and 25 studies from North America. The remainder of the countries, comprising Brazil, Argentina, Panama, South Africa, Australia, and New Zealand, consisted of approximately 5% of the included studies. Of the 122 prevalence studies, 63 studies were conducted in Europe, 38 studies in Asia and the Middle East, and 18 studies in North America. The remainder of the countries, comprising Argentina, Australia, and New Zealand, consisted of less than 5% of the included studies.

Figure 1.

Literature search results.

The annual incidence rates varied by geographic region, with UC estimates ranging from 0.6 to 24.3 per 100,000 in Europe, 0.1 to 6.3 per 100,000 in Asia and the Middle East, and 0 to 19.2 per 100,000 in North America and CD estimates ranging from 0.3 to 12.7 per 100,000 in Europe, 0.04 to 5.0 per 100,000 in Asia and the Middle East, and 0 to 20.2 per 100,000 in North America. These included incidence rates ranging from 1930 to 2008 for European studies, 1950 to 2008 for Asian and Middle Eastern studies, and 1920 to 2004 for North American studies. For prevalence studies, the UC estimates ranged from 4.9 to 505 per 100,000 in Europe, 4.9 to 168.3 per 100,000 in Asia and the Middle East, and 37.5 to 248.6 per 100,000 in North America, and the CD estimates ranged from 0.6 to 322 per 100,000 in Europe, 0.88 to 67.9 per 100,000 in Asia and the Middle East, and 16.7 to 318.5 per 100,000 in North America. Incidence rates and/or prevalence values, including references, for each specific study are presented in Appendix 2 and Appendix 3 , respectively.

Incidence rates stratified by sex were reported in 50 UC and 59 CD studies. The female to male ratio varied from 0.51 to 1.58 for UC studies and 0.34 to 1.65 for CD studies, suggesting that the diagnosis of IBD was not sex specific. Exact sex-stratified incidence rates and ratios, including references, are reported in  Appendix 4 . Additionally, 108 studies reported incidence rates stratified by age, with 69 studies (50 CD studies and 47 UC studies) stratifying incidence by decade. Most CD and UC studies showed peak incidence in the second to fourth decade, with 78.0% of CD studies and 51.1% of UC studies reporting the highest incidence among 20 to 29 year olds. A second modest rise in incidence in latter decades of life was reported in less than one third of CD and UC studies. The age distributions for incidence of CD and UC stratified by sex, including references, are reported in Appendix 5 .

Table 1 describes the ranges in incidence and prevalence stratified into quintiles for CD and UC. Figure 2AC and Figure 3AC show the incidence rates and/or prevalence for CD and UC stratified by quintile levels ( Table 1 ) for geographic regions in the following periods: (1) before 1960, (2) 1960 to 1979, and (3) 1980 to 2006. Before 1960, the only published incidence rates were from Europe and North America, with the exception of one study from Japan. After 1980, a number of studies were published from Asia, South America, and Africa; however, incidence and prevalence data were lacking from many developing nations. Global maps illustrating only incidence rates and only prevalence values are presented in Appendix 6 and Appendix 7 , respectively.

Figure 2.

Worldwide CD incidence rates and/or prevalence for countries reporting data (A) before 1960, (B) from 1960 to 1979, and (C) after 1980. Incidence and prevalence values were ranked into quintiles representing low (dark and light blue) to intermediate (green) to high (yellow and red) occurrence of disease.

Figure 3.

Worldwide UC incidence rates and/or prevalence for countries reporting data (A) before 1960, (B) from 1960 to 1979, and (C) after 1980. Incidence and prevalence values were ranked into quintiles representing low (dark and light blue) to intermediate (green) to high (yellow and red) occurrence of disease.

Temporal trends of incidence rates in the 57 CD and 50 UC studies that reported at least 10 years of data and with at least 3 incidence rate estimates are presented in Figure 4A and B, respectively. Of these studies, 43 (75%) and 30 (60%) had statistically significant (P < .05) increasing incidence rates for CD and UC, respectively. Among studies that showed a significant rise in incidence, the average annual percentage change ranged from 1.2% to 23.3% in CD and 2.4% to 18.1% in UC ( Appendix 2 ). In contrast, 0 CD and 3 (6.0%) UC studies showed statistically significant decreasing incidence rates. Among studies conducted after 1980, 56% of CD studies and 29% of UC studies had increased incidence rates that were statistically significant (P < .05). Studies from Cardiff in the United Kingdom and Olmsted County in the United States showed a significantly consistent increasing incidence of IBD with estimates reported from the 1930s to the end of the 20th century.

Figure 4.

Temporal trends of incidence rates for studies that reported at least 10 years of data and with at least 3 time points for (A) CD and (B) UC.

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