Geographic Distribution of Gastroenterologists and Patients With Inflammatory Bowel Disease in the United States

We aimed to map the distribution of patients with inflammatory bowel disease (IBD) and gastroenterologists throughout the United States and identify local-level and state-level variations in the availability of specialist care.

For each first 3-digit ZIP code tabulation area (ZCTA) and state in the United States, we calculated the density of patients with IBD (Crohn's disease or ulcerative colitis) per 100,000 population, gastroenterologists per 100,000 population, and gastroenterologists per 100 patients with IBD. We used 2022 claims data to identify patients with IBD, the 2022 National Provider Identifier registry for provider details, and the 2020 US Census for area-level variables.

Overall, 520,020 patients with IBD and 21,611 gastroenterologists were identified. Patient density varied across states, from 58.2 (New Mexico) to 337.1 (Maine). On average, there were 4.2 (ranging from 1.4 in Kansas to 9.8 in Hawaii) gastroenterologists/100 patients with IBD. The Midwest and the Southwest Border regions had the lowest density of gastroenterologists. Across the United States, 130 3-digit ZIP code tabulation areas (ZCTA) had zero gastroenterologists/100 patients; 62% of these ZIP codes were in rural areas, and 25% had household income <150% of the poverty line. ZIP codes with ≥5 gastroenterologists/100,000 population tended to have lower poverty rates and were more urban than those with 1 to <5 gastroenterologists/100,000 population.

Geographic disparities in the availability of gastroenterologist care exist at the state and local levels. This disparity was highlighted for patients with IBD and populations living in rural and high-poverty areas.