Fig. 2

(Upper left panel) Relationship between the ABCD classification method with the age of COPD patients. (Lower left panel) Relationship between the ABCD classification method with the time passed since the initial diagnosis of COPD patients. (Upper right panel) Relationship between the ABCD classification method with the number of other, comorbid conditions of COPD patients. (Lower right panel) Relationship between the ABCD classification method with the severity of the disease of COPD patients. COPD: chronic obstructive pulmonary disease, SD: standard deviation, YoA: years of age, YsD: years since diagnosis. * p ≤ 0.01, ** p ≤ 0.00