MMP1 and chronic obstructive pulmonary disease: Combined results indicated significant association of MMP-9 -1562C/T with an increased risk of COPD using a dominant model (OR: 1.46, 95% CI: 1.02–2.08; p = 0.04), However, no association was found between MMP-1 -1607G/GG and the risk of COPD.