Table 5 Standardised incidence ratios and 95% CI of developing Crohn's disease by time since appendectomy stratified by Crohn's disease extent.

Time since appendectomy (years)	Crohn's ileitis SIR (95% CI)	Ileocolonic Crohn's disease SIR (95% CI)	Crohn's colitis SIR (95% CI)	Other and unspecified Crohn's disease SIR (95% CI)
<0.5	14.14 (11.00 to 18.18)	8.43 (4.99 to 14.23)	9.46 (6.10 to 14.66)	6.87 (5.04 to 9.36)
0.5–<1	4.09 (2.57 to 6.48)	1.77 (0.57 to 5.49)	2.79 (1.25 to 6.21)	4.05 (2.71 to 6.04)
1–4	1.84 (1.46 to 2.32)	1.57 (1.04 to 2.36)	1.61 (1.13 to 2.30)	2.28 (1.90 to 2.73)
5–9	1.16 (0.90 to 1.48)	1.61 (1.15 to 2.27)	1.29 (0.92 to 1.81)	1.47 (1.22 to 1.78)
10–14	1.25 (0.99 to 1.58)	0.81 (0.50 to 1.30)	0.56 (0.36 to 0.92)	1.05 (0.85 to 1.31)
15–19	0.76 (0.54 to 1.06)	1.03 (0.64 to 1.66)	1.02 (0.69 to 1.50)	1.15 (0.92 to 1.44)
⩾20	1.01 (0.74 to 1.38)	1.35 (0.86 to 2.11)	0.83 (0.54 to 1.29)	1.17 (0.94 to 1.47)

SIR, standardised incidence ratio.