Background: This study was designed to assess time trends in the incidence of ulcerative colitis and indeterminate colitis in an urban population.
Methods: Medical records of in- and out-patients with inflammatory bowel disease were reviewed by a panel to establish the diagnosis. All histopathologic specimens and almost all radiographs were re-examined.
Results: During the time period 1958 to 1982 there were 354 new cases of definite ulcerative colitis, 117 of probable ulcerative colitis, and 100 of indeterminate colitis. This corresponds to an average annual incidence per 100,000 of 5.5, 1.8, and 1.6, respectively. The incidence was higher in men than in women. Peak incidence was between 20 and 29 years, but indeterminate colitis was most common in 10- to 19-year-old males. The incidence was stable from 1958 to 1972 but then increased in almost all age groups in both sexes. The increase in annual incidence of definite ulcerative colitis from 4.2 to 9.4/10(5) corresponds to an average annual increase of about 5% (p < 0.001). The increase in the incidence of definite ulcerative colitis was due to an increased proportion of patients with proctitis.
Conclusions: This study has shown an increased incidence of ulcerative colitis and indeterminate colitis, and we have found no reason to believe that this is a spurious finding.