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.