Table 3.

Comparison of admission rates before and after appendicectomy, stratified by time since onset of ulcerative colitis (UC). The analysis is based only on subjects from the index cohort

Time since UC onset (y)	Before appendicectomy			After appendicectomy			After/before appendicectomy
	No of UC admissions	Follow up (person years)	Incidence rate	No of UC admissions	Follow up (person years)	Incidence rate	Rate ratios	Confidence intervals
0–2	83	177	0.47	7	24	0.3	0.62	0.24–1.34
2–4	19	145	0.13	8	54	0.15	1.13	0.43–2.70
4–6	33	216	0.15	31	160	0.19	1.26	0.75–2.14
6–8	22	203	0.11	34	273	0.12	1.14	0.65–2.06
8–10	10	125	0.08	17	262	0.06	0.82	0.35–2.00
⩾10	4	87	0.05	20	450	0.04	0.97	0.32–3.90
All person time	171	953	NA	117	1221	NA	1.02	0.78–1.35

NA, not applicable.