Table 1.

Participant description

	Baltic		Danish		Norwegian
	cases	controls	cases	controls	cases	Controls
	N = 441	N = 1156	N = 560	N = 796	N = 274	N = 282
Sex distribution
% female	50	51	48	52	48	41
Age at sampling
Median age (years, SD)	44 [17]	40 [12]	49 [16]	43 [11]	39 [15]	32 [7]
Age of diagnosis
Median age (years, SD)	38 [16]		35 [11]		38 [15]
Disease extent, %
Left sided colitis	76		80		69
Extensive colitis	24		20		31
Smoking habits, %
Current	12		17		13
previous	28		36		31
never	60		47		56

In all three panels age- and sex-matched controls have been used.