Demographic characteristics of study patients
| Normal smokers (N=9) | GOLD 1 (N=7) | GOLD 2 (N=9) | GOLD 4 (N=10) | p Value | |
| Men (%) | 44 | 42.8 | 44 | 60 | 0.880 |
| Age | 63.22±11.43 | 69.71±7.39 | 69.11±7.30 | 50.90±5.62 | <0.0001 |
| Pack-years of smoking | 25.67±16.70 | 41.86±23.26 | 44.00±20.15 | 56.40±36.42 | 0.106 |
| SGRQ score | 11.86±17.27 | 31.90±19.35 | 36.79±16.79 | 61.05±15.62 | <0.0001 |
| BMI | 28.76±6.81 | 26.97±4.10 | 26.50±5.23 | 24.88±2.59 | 0.409 |
| FEV1 PD | 104.22±15.50 | 89.00±5.77 | 70.56±5.05 | 21.20±7.96 | <0.0001 |
BMI, body mass index; FEV1 PD, forced expiratory volume in 1 s percentage predicted; NA, not available; SGRQ, St George Respiratory Questionnaire score.