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The Impact of Racial and Ethnic Differences in Inflammatory Bowel Disease Phenotype in the United States

Anita Afzali, MD, MPH

Anita Afzali, MD, MPH
Acting Assistant Professor of Medicine
Director, Inflammatory Bowel Diseases Program
Division of Gastroenterology
UW Medicine - Harborview Medical Center
Seattle, WA, USA

Inflammatory bowel disease (IBD) has become a global disease with a rising incidence in both developed and developing countries. In the United States, nearly 1.5 million patients are affected with IBD, with approximately equal distribution of Crohn’s disease (CD) and ulcerative colitis (UC) 1. Epidemiological studies are mostly in Caucasian populations in North America and Europe, and similarly large efficacy trials,  hospitalizations rates, and surgery outcomes have also included data from predominantly Caucasian populations 2, 3. Consequently, there are limited studies in non-Caucasian populations and the generalizability of information from these studies among other races and ethnic groups affected with IBD is sparse and reported findings are inconsistent. To clarify language, in this paper I will use the terms for race and ethnicity as they are used in each article cited.

In a systematic review by Hou JK, et al. 4, the distribution and manifestations of IBD in non-Caucasian patients were evaluated from 28 studies, including 1,272 Hispanics, 547 African Americans, and 35,844 Asians. The review was limited as most studies were not population based, only 6 were from the USA, and many had small sample sizes. The review concluded that the prevalence and incidence rates of Hispanics and Asians with IBD have increased. Compared to African Americans, there were greater proportions of Hispanics and Asians with UC than with CD. There were differences in disease behavior, with ileocolonic CD reported as the most common location of disease among all three racial/ethnic groups. Fistulizing CD was described in nearly 30% of Hispanics, 25% of African Americans, and up to 50% among Asians. Family history of IBD among affected patients was nearly 20% among Hispanics and African Americans and less commonly positive among Asians (0-10%). Lastly, extra-intestinal manifestations (EIM) included joint complications, which were the most frequently reported EIM among African Americans, Asians, and Hispanics.

Recent efforts to evaluate racial and ethnic variation of patients and regional differences in the prevalence of IBD in the United Studies have been studied using a large nationally representative survey, Medical Expenditure Panel Survey (MEPS) during 1996-2007 5. Among 202,468 people surveyed, 316 were diagnosed with IBD (including 26 Blacks, 21 Hispanics, and 5 Asians). The prevalence of IBD, both UC and CD, was higher in Whites than Blacks, Hispanics, and Asians.

At the University of Chicago, a cross-sectional review was performed from January 2008 to 2013 to evaluate differences between Whites and African Americans 6. The study included 1,235 patients with CD (91% White and 9% African American) and 541 with UC (95% White and 5% African American). African American patients with UC were diagnosed at an older mean age and shorter mean duration of disease. Family history of IBD was similar. African American patients with CD had less ileal involvement (p<0.01) and more Crohn’s-related surgeries compared to Whites. Otherwise, there were no significant differences in disease location. This study also looked at EIMs, and found that significantly more African American patients with IBD had arthralgias and a higher prevalence of ankylosing spondylitis and sacroiliitis (p=0.035). The rates of other EIMs, including erythema nodosum (EN), pyoderma gangrenosum (PG), oral aphthous ulcers, ocular inflammation, osteoporosis, liver disease, and primary sclerosing cholangitis (PSC), were similar in both groups.

These results about EIMs are similar to a large North American cohort study of patients recruited from six academic centers including the United States and Canada 7 except that African Americans had more than a four-fold greater prevalence of uveitis. Unlike the prior study, African Americans were less likely to have Crohn’s-related surgeries. African Americans were less likely to have penetrating CD. There were no significant differences reported in patients with UC.

IBD phenotypic characteristics between Hispanics and non-Hispanic Whites in the United States was also described in a large cohort study of 325 patients (64% Hispanics), and also compared between US-born and foreign-born Hispanics 8. Hispanics were diagnosed with IBD at an older age, were less likely to have a family history, and were more likely to have UC than CD, although UC was more common in foreign-born Hispanics compared to US-born Hispanics and Whites. CD extent was similar among races, with most patients developing ileocolonic CD. There were no differences in EIM incidence among the groups in this study. Lastly, non-Hispanic Whites had a higher incidence rate of IBD-related surgical events compared to Hispanics (p<0.01).

Older studies report that perianal disease has a higher prevalence among Hispanics compared to Whites and a higher prevalence of surgery for chronic UC and a much higher rate of colectomy 7.

More recently, Nguyen et al. described the burden of IBD among different races utilizing the Nation-wide Inpatient Sample to ascertain rates of IBD-related hospitalizations and underlying cause of death to assess IBD-related mortality. An estimated 1,810,773 adults in the United States were affected by IBD, a prevalence of 908/100,000. IBD was more common in non-Hispanic Whites compared to non-Hispanic Blacks and Hispanics. The incidence of IBD was also similarly higher in non-Hispanic Whites compared to non-Hispanic Blacks and Hispanics. There was a disproportionate higher ratio of hospitalizations, surgery, and IBD-related mortality among non-Hispanic Blacks compared with the other racial groups.

In conclusion, there are racial differences in IBD phenotype in the adult population in the United States. These differences have implications in the diagnosis, management, and treatment of disease as well as complications of disease. Increased awareness and improved characterization of disease phenotypes among different ethnicities will facilitate timely diagnosis of disease, including understanding of which races may be at an increased risk for perianal disease, upper gastrointestinal involvement, and EIMs. Further research efforts and observational studies are needed to help us better understand disease patterns in these understudied populations in the United States.


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