MMP12 and chronic obstructive pulmonary disease: On comparing the genotype frequency of MMP2 rs243864, G/G homozygote genotype (G/G vs T/G + T/T, cOR = 5.83; 95% CI, 1.19–28.4, p = 0.029) and MMP12 rs652438, T/T homozygote genotype (T/T vs T/C + C/C, cOR = 1.79; 95% CI, 1.16–2.76, p = 0.008) were significant to increased risk of COPD in recessive model.