Comparison of baseline characteristics.

All values expressed as Mean (standard error, SE). BMI = Body mass index; FEV1 = Forced expiratory volume in 1 second; FVC = Forced vital capacity; MMRC = Modified Medical Research Council Dyspnea Scale; BODE = Body-Mass Index, Airflow Obstruction, Dyspnea, and Exercise Capacity Index; TLC = Total lung capacity; FRC = Functional residual capacity. **significant difference compared to non smokers at p<0.001. *significant difference compared to non smokers at p<0.01. significant difference compared to smokers at p<0.001.