Background: The incidence of microscopic colitis (MC) has increased in several centers, but long-term epidemiologic data are missing. We report an epidemiologic study of collagenous colitis (CC) and lymphocytic colitis (LC) during 1999–2008, as a follow-up of our previous studies 1984–1998.
Methods: Population-based study of residents of the catchment area of the hospital, with a new diagnosis of MC between 1999 and 2008. Patients were identified by diagnosis registers of the Departments of Medicine and Pathology. Medical files were reviewed, and colonic biopsies were reevaluated.
Results: Collagenous colitis was diagnosed in 96 patients (75 females) and LC in 90 patients (74 females). The mean annual age-standardized incidence (per 100,000 inhabitants) was MC 10.2 (95% confidence interval: 8.7–11.7), CC 5.2 (4.2–6.3), and LC 5.0 (4.0–6.0). Age-specific incidence showed a peak in females older than 70 years. Prevalence (per 100,000 inhabitants) on December 31, 2008, was MC 123 (107.6–140.0), CC 67.7 (56.4–80.6), and LC 55.3 (45.2–67.1). A comparison of current study period with 1993–1998 showed unchanged mean incidence of MC, but a 2-fold increase in women older than 60 years with LC (standardized rate ratios 2.2, [1.2–3.7]) and increased female to male ratio (4.6:1 versus 2.1:1; P = 0.02) in LC.
Conclusions: After an initial rise during 1980s and early 1990s, annual incidence of CC and LC has been stable during the last 15 years around 5/100,000 inhabitants for each disorder. The increasing incidence in older women with LC may be related to an increasing proportion of older individuals in the background population and increased colonoscopy frequency in elderly.