Table 4.
Results of subgroup analyses and meta-regression based on study location
| Type of IBD | Country | RR (95% CI) | Heterogeneity | Number of studies | Number of participants | Subgroup differences | Residual heterogeneity |
|---|---|---|---|---|---|---|---|
| Crohn’s Disease | Canada | 1.34 (1.24–1.45) | I2 = 64% | 3 | 588,067 | p < 0.0001 REF |
I2 = 33% R2 = 92% p = 0.16 |
| Finland | 2.33 (1.41–3.86) | – | 1 | 1165 | β 0.55 (0.036 to 1.07) | ||
| Israel | 0.78 (0.55–1.10) | – | 1 | 47 | β −0.54 (−0.91 to −0.17) | ||
| New Zealand | 1.46 (1.07–1.99) | – | 1 | 1238 | β 0.087 (−0.25 to 0.42) | ||
| Sweden | 1.61 (1.41–1.83) | I2 = 0% | 2 | 148,347 | β 0.18 (0.0014 to 0.35) | ||
| Taiwan | 1.50 (1.31–1.72) | – | 1 | 25,799 | β 0.11 (−0.071 to 0.30) | ||
| United Kingdom | 0.90 (0.83–0.97) | I2 = 0% | 4 | 1351 | β −0.39 (−0.54 to −0.25) | ||
| United States | 1.39 (1.13–1.71) | I2 = 47% | 2 | 57,159 | β 0.062 (−0.10 to 0.23) | ||
| Ulcerative colitis | Canada | 1.28 (1.03–1.60) | I2 = 98% | 3 | 583,902 | p < 0.0001 REF |
I2 = 96% R2 = 0% p < 0.0001 |
| Chile | 0.90 (0.77–1.06) | – | 1 | 226 | β −0.35 (−0.80 to 0.099) | ||
| Finland | 1.11 (0.68–1.81) | – | 1 | 1810 | β −0.14 (−0.79 to 0.50) | ||
| Italy | 1.61 (1.25–2.07) | I2 = 84% | 2 | 182 | β 0.22 (−0.13 to 0.57) | ||
| Japan | 0.73 (0.32–1.68) | – | 1 | 768 | β −0.56 (−1.50 to 0.37) | ||
| New Zealand | 0.93 (0.67–1.29) | – | 1 | 1253 | β −0.32 (−0.85 to 0.21) | ||
| Sweden | 1.54 (1.37–1.74) | – | 1 | 148,295 | β 0.18 (−0.26 to 0.62) | ||
| Taiwan | 1.46 (1.03–2.07) | – | 1 | 21,541 | β 0.13 (−0.42 to 0.68) | ||
| United Kingdom | 1.29 (1.09–1.54) | I2 = 66% | 3 | 2010 | β 0.031 (−0.31 to 0.37) | ||
| United States | 1.32 (1.07–1.62) | I2 = 41% | 2 | 59,727 | β 0.0018 (−0.37 to 0.37) |