Methodology for high-quality studies on course and prognosis of inflammatory bowel disease

Table 1 Population-based prospective and retrospective studies

Study	Population size	Inception period	UC	CD	Surgery UC	Surgery CD	Mortality UCSMR (95% CI)	Mortality CDSMR (95% CI)
Prospective studies
Copenhagen[2-7], Denmark	550 000	1962-1987	1160	374	24%	61%	1.1 (1-1.2)	1.3 (1.1-1.6)
		1991-1993	89	58	24%	65%	1.5 (0.9-2.5)	2.3 (1.1-4.2)
	1 211 634	2003-2004	326	209	-	-	0.9 (0.3-2.4)	0.8 (0.02-4.2)
		1962-2004	1575	641
EC-IBD study[12-17]	NA	1991-1993	1379	706	8.70%	40%-55%	1.09 (0.86-1.37)	1.85 (1.3-2.55)
		1991-2004	-	365
IBSEN[23-28], Norway	970 000	1990-1993	525	225	9.8% (7.4-12.4)	37.9% (31.4-44.4)	Survival 96%	Survival 96%
Retrospective studies
Stockolm[29-31], Sweden	1 200 000	1955-1984	1547	1251	28.00%	71%	1.37 (1.2-1.54)	1.51 (1.29-1.75)
		1955-2000	-	20 120		78% (15 yr)	(15 yr)	(15 yr)
	1 470 000	1990-2001	-	1389
Uppsala[32,33], Sweden	1 200 000	1965-1983	2509	1469	-	96% (15 yr)	1.4 (1.2-1.5)	1.6 (1.4-1.9)
Olmsted[8-11], United States	110 000	1940-1993	278	225	49.00%	49%	0.8 (0.6-1)	1.2 (0.9-1.6)
	124 000	1940-2000	372	308
Leicester[34,35], United Kingdom	930 000	1972-1989	1014	610	-	-	0.9 (0.8-1.1)	0.72 (0.5-1)
Florence[21,22], Italy	650 000	1978-1992	689	231	-	-	0.7 (0.56-0.88)	1.51 (1.06-2.08)
Cardiff[36-41], Wales	280 000	1986-1991	-	105	-	59%	-
		1992-1997		99		37%
	NA	1998-2003		137		25%
		1941-2000		394				1.29 (1.12-1.45)
Leiden[41], The Netherlands	440 000	1979-1983	-	210	-	56% (15 yr)	-	2.23 (1.75-2.85)

UC: Ulcerative colitis; CD: Crohn's disease; SMR: Standardized mortality ratio; EC-IBD study: European collaborative study on inflammatory bowel disease; IBSEN: Inflammatory bowel south-eastern Norway; NA: Not available. Number of cases may vary between various reports from same centers.