About the Epidemiology of IBD

Epidemiology is the study of the frequency and distribution of diseases in the population.

It is estimated that up to one million Americans suffer from Crohn's disease or ulcerative colitis (collectively known as inflammatory bowel diseases, or IBD). The search for risk factors in IBD has been frustrating, and the difficulty in diagnosing these diseases has been a further hindrance. However, epidemiologists have gathered enough information to know a good deal about the distribution of IBD in the United States and Western Europe. Current evidence suggests that both genetic and environmental factors contribute to these diseases.

Genetics

In 2001, Nod2, the first gene linked to Crohn's disease, was discovered. This breakthrough was funded in part by a CCFA research grant. Most researchers agree that there is a strong genetic component in IBD. If a person has a relative with the disease, his/her risk is estimated to be at least 10 times that of the general population -- 30 times greater if the relative is a sibling. New technologies, including a genome-wide search, are helping researchers to close in on the genes that predispose people to IBD.

Race and Ethnicity

• American Jews of European descent are four to five times more likely to develop IBD than the general population.
• IBD has long been considered a predominantly white disease. The prevalence rate among whites is 149 per 100,000. Among African Americans, however, there has been a steady increase in reported cases of both Crohn's disease and ulcerative colitis. An HMO with two million members reported hospitalization rates per 100,000 by race, over a six-year period, as:
  
  
           10.2 - Whites
           10.2 - African Americans
  
  According to this study, prevalence rates among Hispanics and Asians were lower than those for whites and African Americans.

Gender

The incidence of IBD does not appear to be significantly different between men and women.

Age

• IBD can begin at any age, but adolescents and young adults between the ages of 15 and 35 are most susceptible.
  
  
• Ten percent, or an estimated 100,000, of those afflicted are youngsters under the age of 18.
  
  
• After age 50, there is a smaller second wave of new cases.

Environment

For reasons not yet known, IBD is largely a disease of the developed world (principally, the U.S. and Europe). Similarly, Crohn's disease and ulcerative colitis are reported to be more common in urban than in rural areas, and in northern than in southern climates. Frequency of disease increases when populations move from underdeveloped to developed countries, and vice versa.

Diet

There is no known link between eating certain kinds of foods and getting IBD, but dietary modifications, especially during severe flare-ups, can help reduce disease symptoms and replace lost nutrients.