Table 1 reports the main anthropometric, functional, and clinical data of the study population. No statistically significant differences were observed among the four groups; we have not performed statistical analysis on FEV1 values, mMRC, and CAT scores, because they differ by definition among the four groups, since the 2011 GOLD document specifically divides COPD patients according to FEV1 and symptoms (mMRC and CAT) values [5]. The gene discussed is CAT; the disease is chronic obstructive pulmonary disease.