An epidemiological study of collagenous colitis in southern Sweden from 2001-2010.

AIM: To estimate the incidence of collagenous colitis (CC) in southern Sweden during 2001-2010.
METHODS: Cases were identified by searching for CC in the diagnostic registers at the Pathology Departments in the county of Skåne. The catchment area comprised the south-west part of the county (394 307 inhabitants in 2010) and is a mixed urban and rural type with limited migration. CC patients that had undergone colonoscopy during the defined period and were living in this area were included in the study regardless of where in Skåne they had been diagnosed. Medical records were scrutinized and uncertain cases were reassessed to ensure that only newly diagnosed CC cases were included. The diagnosis of CC was based on both clinical and histopathological criteria. The clinical criterion was non-bloody watery diarrhoea. The histopathological criteria were a chronic inflammatory infiltrate in the lamina propria, a thickened subepithelial collagen layer ≥ 10 micrometers (μm) and epithelial damage such as flattening and detachment.
RESULTS: During the ten year period from 2001-2010, 198 CC patients in the south-west part of the county of Skåne in southern Sweden were newly diagnosed. Of these, 146 were women and 52 were men, i.e., a female: male ratio of 2.8:1. The median age at diagnosis was 71 years (range 28-95/inter-quartile range 59-81); for women median age was 71 (range 28-95) years and was 73 (range 48-92) years for men. The mean annual incidence was 5.4/10(5) inhabitants. During the time periods 2001-2005 and 2006-2010, the mean annual incidence rates were 5.4/10(5) for both periods [95% confidence interval (CI): 4.3-6.5 in 2001-2005 and 4.4-6.4 in 2006-2010, respectively, and 4.7-6.2 for the whole period]. Although the incidence varied over the years (minimum 3.7 to maximum 6.7/10(5)) no increase or decrease in the incidence could be identified. The odds ratio (OR) for CC in women compared to men was estimated to be 2.8 (95% CI: 2.0-3.7). The OR for women 65 years of age or above compared to below 65 years of age was 6.9 (95% CI: 5.0-9.7), and for women 65 years of age or above compared to the whole group the OR was 4.7 (95% CI: 3.6-6.0). The OR for age in general, i.e., above or 65 years of age compared to those younger than 65 was 8.3 (95% CI: 6.2-11.1). During the last decade incidence figures for CC have also been reported from Calgary, Canada during 2002-2004 (4.6/10(5)) and from Terrassa, Spain during 2004-2008 (2.6/10(5)). Our incidence figures from southern Sweden during 2001-2010 (5.4/10(5)) as well as the incidence figures presented in the studies during the 1990s (Terrassa, Spain during 1993-1997 (2.3/10(5)), Olmsted, United States during 1985-2001 (3.1/10(5)), Örebro, Sweden during 1993-1998 (4.9/10(5)), and Iceland during 1995-1999 (5.2/10(5)) are all in line with a north-south gradient, something that has been suggested before both for CC and inflammatory bowel disease.
CONCLUSION: The observed incidence of CC is comparable with previous reports from northern Europe and America. The incidence is stable but the female: male ratio seems to be decreasing.