Evolution of the Incidence of Collagenous Colitis and Lymphocytic Colitis in Terrassa, Spain: A Population-based Study

Background: Previous studies suggest an increase in the incidence rate of microscopic colitis in recent decades. The aim was to evaluate changes in the population-based incidence rate of microscopic colitis and its subtypes over time in Terrassa, Spain. Methods: This was a prospective study during the period 2004-2008, with a comparison of data from the period 1993-1997. The catchment area was a mixed rural-urban type, with nearly 290,000 inhabitants. All patients with nonbloody chronic diarrhea referred for a diagnostic colonoscopy were included. Multiple biopsy specimen samples were obtained when the macroscopic appearance of the colonic mucosa was normal to rule out microscopic colitis. Crude and adjusted incidence rates based on either the year of diagnosis or the date of onset of symptoms were calculated. Results: Forty patients with collagenous colitis (CC) and 32 with lymphocytic colitis (LC) were identified. The mean annual incidence of CC and LC based on the year of onset of symptoms was 2.6/10(5) inhabitants (95% confidence interval [CI], 1.9-3.3), and 2.2/10(5) inhabitants (95% CI, 1.5-3.0), respectively. Incidence rates for CC based on the year of onset of symptoms were significantly higher in the period 2004-2008 than in 1993-1997 (2.6 versus 1.1/10(5); P = 0.012). The increase in CC incidence was more marked in women (P = 0.047) than in men (P = 0.19). Conclusions: The annual incidence of CC in Terrassa increased over time, mainly in women. Nevertheless, the rates were much lower than those observed in northern Europe, suggesting that there is a north-south difference in the incidence of microscopic colitis.