Association of Inflammatory Bowel Disease with Incident… : Clinical Journal of the American Society of Nephrology
sing a large-scale epidemiological cohort. Methods We retrospectively analyzed 4,311,393 adults enrolled in the JMDC Claims Database (previously known as the Japan Medical Data Center database), a nationwide epidemiological database in Japan. The definitions of IgA nephropathy and inflammatory bowel disease (ulcerative colitis or Crohn’s disease) were based on International Classification of Diseases-10th Revision codes. Individuals who had a prior history of IgA nephropathy were excluded. Study participants were categorized into two groups according to the presence of inflammatory bowel disease. Clinical outcomes were collected between January 2005 and May 2022. The primary outcome was incident IgA nephropathy. Results Median (interquartile range) age was 44 (36-53) years, and 2,497,313 (58%) were men. Inflammatory bowel disease was observed in 18,623 individuals (0.4%). Over a median follow-up of 1,089 (532–1,797) days, there were 2,631 incidences of IgA nephropathy and 22 incidences