Main results of the meta-analysis
| Studies (n) | Comparison model | Test of association | Test of heterogeneity | P value for publication bias | |||||
| OR | 95% CI | P value | Q | P value | I2 (%) | Begg’s test | Egger’s test | ||
| 3 | C vs T | 1.50 | 0.90 to 2.49 | 0.121 | 16.52 | 0.001 | 87.9 | 0.602 | 0.422 |
| 3 | CC vs TT | 2.02 | 0.58 to 6.99 | 0.269 | 7.49 | 0.024 | 73.3 | ||
| 3 | CT+CC vs TT | 1.78 | 0.60 to 5.32 | 0.299 | 2.96 | 0.052 | 66.2 | ||
| 3 | CC vs CT+TT | 1.53 | 0.89 to 2.63 | 0.124 | 5.92 | 0.001 | 86.3 | ||
CI, confidence interval; OR, odd ratio.