Table 3.

Incidence rate ratio by timing of antibiotic course

Age group	Most recent antibiotic use	IRR*, IBD	IRR lower bound, IBD	IRR upper bound, IBD	IRR*, CD	IRR lower bound, CD	IRR upper bound, CD	IRR*, UC	IRR lower bound, UC	IRR upper bound, UC
10–40 years	No use in the last 5 years	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00
10–40 years	4 to 5 years	1.13	1.08	1.20	1.12	1.03	1.23	1.14	1.06	1.21
10–40 years	3 to 4 years	1.18	1.13	1.24	1.23	1.14	1.33	1.15	1.09	1.22
10–40 years	2 to 3 years	1.24	1.19	1.29	1.34	1.26	1.43	1.18	1.12	1.24
10–40 years	1 to 2 years	1.40	1.35	1.44	1.59	1.51	1.68	1.28	1.23	1.34
40–60 years	No use in the last 5 years	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00
40–60 years	4 to 5 years	1.21	1.13	1.29	1.22	1.07	1.39	1.21	1.12	1.31
40–60 years	3 to 4 years	1.36	1.29	1.44	1.36	1.22	1.52	1.37	1.28	1.46
40–60 years	2 to 3 years	1.41	1.34	1.48	1.53	1.39	1.68	1.37	1.29	1.45
40–60 years	1 to 2 years	1.66	1.59	1.73	1.89	1.75	2.04	1.58	1.51	1.66
60+years	No use in the last 5 years	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00
60+years	4 to 5 years	1.22	1.14	1.31	1.23	1.06	1.41	1.22	1.12	1.33
60+years	3 to 4 years	1.26	1.18	1.33	1.29	1.15	1.46	1.25	1.16	1.34
60+years	2 to 3 years	1.39	1.32	1.46	1.37	1.24	1.52	1.41	1.32	1.49
60+years	1 to 2 years	1.63	1.57	1.70	1.72	1.58	1.86	1.62	1.54	1.70

^*Adjusted for sex, calendar time, antiviral and antifungal exposure, proton pump inhibitor exposure, socioeconomic index and population density.

CD, Crohn’s disease; IBD, inflammatory bowel disease; IRR, incidence rate ratio; UC, ulcerative colitis.