MMP9 and chronic obstructive pulmonary disease: In the multiple linear regression, the association between the serum MMP-9 levels and T90 was statistically significant after adjusting for BMI, smoking status, and comorbidities such as hypertension, diabetes mellitus, COPD, and asthma in the patients with OSA (β = 0.53, standard error [SE] = 0.21, p = 0.013; Table 3).