Standardised incidence ratios and 95% CI of developing Crohn’s disease by the time since appendectomy, stratified by cause of appendectomy
| Time since appendectomy (years) | Overall SIR (95% CI) | Appendicitis or mesenteric lymphadenitis SIR (95% CI) | Perforated appendicitis SIR (95% CI) | Non-perforated appendicitis SIR (95% CI) | Mesenteric lymphadenitis SIR (95% CI) | Non-inflamed appendix* SIR (95% CI) |
|---|---|---|---|---|---|---|
| SIR, Standardised incidence ratio. | ||||||
| *Non-inflamed appendix includes appendectomy patients without appendicitis or mesenteric lymphadenitis. | ||||||
| <0.5 | 8.69 (7.68 to 9.84) | 7.16 (6.08 to 8.44) | 12.12 (8.92 to 16.46) | 6.10 (4.99 to 7.46) | 6.93 (3.30 to 14.53) | 12.12 (10.03 to 14.63) |
| 0.5–<1 | 3.16 (2.58 to 3.89) | 2.85 (2.20 to 3.69) | 5.99 (3.86 to 9.28) | 2.11 (1.50 to 2.97) | 3.78 (1.42 to 10.06) | 3.89 (2.78 to 5.44) |
| 1–4 | 1.86 (1.69 to 2.05) | 1.66 (1.47 to 1.87) | 2.38 (1.85 to 3.05) | 1.42 (1.22 to 1.64) | 2.86 (1.99 to 4.12) | 2.36 (2.02 to 2.76) |
| 5–9 | 1.25 (1.12 to 1.39) | 1.15 (1.01 to 1.31) | 1.23 (0.88 to 1.70) | 1.12 (0.96 to 1.30) | 1.31 (0.86 to 2.01) | 1.51 (1.25 to 1.81) |
| 10–14 | 1.03 (0.91 to 1.17) | 0.88 (0.75 to 1.03) | 1.28 (0.90 to 1.82) | 0.73 (0.59 to 0.89) | 1.45 (0.97 to 2.17) | 1.44 (1.17 to 1.77) |
| 15–19 | 0.98 (0.84 to 1.15) | 0.85 (0.69 to 1.03) | 1.05 (0.65 to 1.68) | 0.81 (0.64 to 1.03) | 0.80 (0.43 to 1.50) | 1.31 (1.02 to 1.69) |
| ⩾20 | 1.09 (0.93 to 1.27) | 1.01 (0.82 to 1.23) | 0.84 (0.45 to 1.55) | 0.96 (0.76 to 1.22) | 1.48 (0.91 to 2.41) | 1.25 (0.97 to 1.61) |