Table 1

Baseline characteristics of the study population

Patients with COPD (n=262)Healthy smokers (n=152)
Age† (years)66 (60–72)61 (58–65)*
Gender (M/F)215/49120/32
Body mass index (kg/m2)25.3±4.826.9±4.1*
Previous steroid use, n (%)81 (31)0
Current steroids, n (%)35 (13)0
Current smoker, n (%)125 (47)68 (44)
Pack-years†47 (33–63)39 (30–52)*
Quit-years†1 (0–8)2 (0–8)
Pulmonary function tests
FEV1, litres1.8±0.93.2±0.8*
FEV1, % predicted61±27104±15*
FVC, litres3.4±1.04.1±0.9*
FVC, % predicted93±22110±14*
DLCO, % predicted60±2185±15*
KCO, % predicted78±2396±16*
25-OHD (ng/ml)19.9±8.224.6±8.7*
GOLD class 1, n (%)70 (27)0
GOLD class 2, n (%)87 (33)0
GOLD class 3, n (%)75 (29)0
GOLD class 4, n (%)30 (11)0
  • Demographic, smoking and pulmonary function characteristics of patients with COPD and smoking controls are shown. Data are expressed as numbers (group percentages in parentheses) for categorical variables and mean values±SD for continuous variables. When variables were not normally distributed, median values (Q1–Q3 IQR in parentheses) are given instead (indicated by †). Significant p values are indicated by an asterisk (*p<0.05).

  • COPD, chronic obstructive pulmonary disease; DLCO, diffusing capacity of the lung for carbon monoxide; F, female; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; GOLD, Global Initiative for Obstructive Lung Disease; KCO, alveolar ventilation; M, male; 25-OHD, 25-hydroxyvitamin D.