Table 1. Observed and expected numbers of colon cancers, including rectosigmoid cancers, and corresponding standardised incidence ratios in patients with irritable bowel syndrome overall and by period of follow-up, gender, age at diagnosis, and calendar period of diagnosis.

	All 57 851 IBS patients			19 150 IBS patients with known colonoscopya
	Observed cancers, N	Expected cancers, N	SIR (95% CI)	Observed cancers, N	Expected cancers, N	SIR (95% CI)
Total	407	358.6	1.14 (1.03–1.25)	56	54.3	1.03 (0.78–1.34)
Follow-up
⩽3 months	64	7.6	8.42 (6.48–10.75)	26	2.4	10.77 (7.03–15.78)
4–12 months	34	22.8	1.49 (1.03–2.08)	3	7.1	0.42 (0.09–1.24)
2nd and 3rd year	62	57.4	1.08 (0.83–1.39)	9	16.6	0.54 (0.25–1.03)
4th and 5th year	41	50.8	0.81 (0.58–1.10)	7	12.5	0.56 (0.22–1.15)
6th to 10th year	89	95.3	0.93 (0.75–1.15)	11	14.1	0.78 (0.39–1.39)
>10 years	117	124.7	0.94 (0.78–1.12)	0	1.6	—
Gender
Women	302	253.1	1.19 (1.06–1.34)	34	35.0	0.97 (0.67–1.36)
Men	105	105.5	1.00 (0.81–1.21)	22	19.3	1.14 (0.71–1.73)
Age
<20 years	0	0.3	—	0
20–39 years	25	16.5	1.52 (0.98–2.24)	5	0.9	5.47 (1.77–12.75)
40–49 years	43	36.7	1.17 (0.85–1.58)	1	3.2	0.31 (0.01–1.73)
50–59 years	88	78.5	1.12 (0.90–1.38)	12	10.7	1.12 (0.58–1.95)
60–69 years	113	107.5	1.05 (0.87–1.26)	13	17.4	0.75 (0.40–1.28)
70–79 years	96	91.3	1.05 (0.85–1.28)	18	16.3	1.10 (0.65–1.74)
⩾80 years	42	27.8	1.51 (1.09–2.04)	7	5.7	1.23 (0.49–2.53)

Abbreviations: IBS=irritable bowel syndrome; CI=confidence interval; SIR=standardised incidence ratio.

^aColonoscopy or flexible sigmoidoscopy.