Table 1 Numbers of cases and controls recruited and numbers included in this analysis (bold figures).

	Cases			Controls
Total numbers of recruited cases and controls	540			614
After exclusion of cases detected by screening	432			614
After exclusion of cases of IBD	432			613

	Determination of history of colonoscopy
	Cases			Controls
Self reported endoscopy of large bowel	Yes		No	Yes		No
	84		346	271		342
After correction of subjects with misreport of endoscopy of	80		350	262		351
large bowel (eg, gastroscopy) according to validation
After exclusion of subjects with endoscopy <1 year ago	74			226
Written report of endoscopy of large bowel available	Yes	No		Yes	No
	49	25		169	57
After exclusion of subjects with sigmoidoscopy or rectoscopy according to medical charts where available, or according to	42	19		142	47
self report otherwise
No detection of polyps according to charts where available,	21	9		103	31
or according to self report otherwise
Total numbers of cases and controls included in analysis	380			485

IBD, inflammatory bowel disease.