IL13 and chronic obstructive pulmonary disease: Using a codominant genetic model, pooled effect size showed an association of IL-13 −1112 C/T with the risk of COPD (TT vs CT, OR: 1.82, 95% CI: 1.14–2.92, Figure 2 and TT vs CC, OR: 2.02, 95% CI: 1.10–3.72, Figure 3), which indicated individuals with TT genotype had a higher risk for COPD than those with CT or CC genotypes.