Figure 4From: Elevation of sputum matrix metalloproteinase-9 persists up to 6 months after smoking cessation: a research study The levels of MMP-9 in the smoking cessation group at the baseline and at 3 and 6 months after stopping smoking. The levels of MMP-9 were significantly higher in the smoking cessation group compared to the non-smokers (p = 0.02). MMP-9 levels remained elevated in the smoking cessation group when compared to the levels of non-smokers at 6 months after the cessation (p = 0.017).Back to article page