Figure 4From: Ageing and smoking contribute to plasma surfactant proteins and protease imbalance with correlations to airway obstruction Relationship between plasma MMP-9 levels and the demographic parameters, age (A), BMI (B), pack-years (C) and FEV1/FVC% of predicted (D), in all of the subjects. ○ = young non-smokers; ● = young smokers; ◊ = middle aged/elderly non-smokers; ♦ = middle aged/elderly smokers; ■ = COPD patients.Back to article page