Fig. 4

Total CAT scores of COPD patients aged <75 and ≥75 years with different GOLD grades of COPD. Gray columns <75 years old, black columns ≥75 years old. Data are presented as mean ± SD. *p < 0.05 between two different age groups. p < 0.0001 comparison between four GOLD grade groups of <75 years old, and ^†p < 0.05 by post hoc analysis between Grade IV vs. I, II, and III groups