Incidence rate ratio for antibiotic exposure
| Age group | Antibiotic exposure | Person-years | Number of IBD cases | 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 | 14 085 774 | 7076 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
| 10–40 years | Yes | 21 832 205 | 15 974 | 1.28 | 1.25 | 1.32 | 1.40 | 1.33 | 1.47 | 1.21 | 1.17 | 1.26 |
| 40–60 years | No | 10 501 835 | 4023 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
| 40–60 years | Yes | 17 312 431 | 10 896 | 1.48 | 1.43 | 1.54 | 1.62 | 1.51 | 1.74 | 1.44 | 1.38 | 1.50 |
| >60 years | No | 7 959 839 | 3572 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
| >60 years | Yes | 15 420 245 | 11 357 | 1.47 | 1.42 | 1.53 | 1.51 | 1.40 | 1.63 | 1.47 | 1.40 | 1.53 |
*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.