HOW COMMON ARE CROHN'S DISEASE AND ULCERATIVE COLITIS?

Most estimates of these diseases in the past have been based on reports from just a few areas. Newer studies, looking at larger populations, show that these diseases are relatively rare, but they are increasing.     

According to a 2013 study (MD Kappelman and others, Digestive Dis Sci pages 519-525) using 2009 statistics from insurance claims in the United States, the number of adults with Crohn's disease (the prevalence) is only 2.4 per thousand. This means that in every 10,000 adults, only 24 will have Crohn's disease and another 26 will have ulcerative colitis (2.6/1000). In children, the numbers are smaller, but Crohn's is almost 2x as common: 5.8 (approximately 6) out of 10,000 children will have Crohn's, compared to the 3.4 who will have ulcerative colitis.

Interestingly, both diseases are less common in the South and West compared to the Northeast and Midwest. This actually may have important implications about cause (and disease management), since sun exposure (and Vitamin D from the sun) are lower in the areas where the disease is more common. Of note, though it's hard to explain, Crohn's disease is less common in girls, but more common in women; while there is no difference in males versus females with ulcerative colitis.

The greater concern is that these Inflammatory Bowel Diseases are increasing.

These statistics, which mean that approximately 1.2 million Americans have IBD (565,000 with Crohn's and 593,000 with ulcerative colitis) seem to be in sync with a Canadian report published in 2006 (CN Bernstein, Amer J Gastroenterology pages 1559-1568). However, European studies are quite different depending on the country and their populations (and perhaps their sun exposure).